Apparatus and method of inserting spinal implants

ABSTRACT

Apparatus and a method of inserting spinal implants is disclosed in which an intervertebral space is first distracted, a hollow sleeve having teeth at one end is then driven into the vertebrae adjacent that disc space. A drill is then passed through the hollow sleeve removing disc and bone in preparation for receiving the spinal implant which is then inserted through the sleeve. Apparatus and a method of inserting spinal implants is disclosed in which an intervertebral space is first distracted to restore the normal angular relationship of the vertebrae adjacent to that disc space. An extended outer sleeve having extended portions capable of maintaining the vertebrae distracted in their normal angular relationship is then driven into the vertebrae adjacent that disc space. A drill is then passed through the hollow sleeve removing disc and bone in preparation for receiving the spinal implant which is then inserted through the sleeve.

RELATED APPLICATIONS

[0001] This application is a continuation in part of U.S. applicationSer. No. 08/074,781 filed on Jun. 10, 1993, which is a continuation inpart of U.S. application Ser. No. 07/205,935, filed on Jun. 13, 1988,which is a division of application Ser. No. 07/205,935 filed on Jun. 3,1988, now U.S. Pat. No. 5,015,247, issued on May 14, 1991, which areincorporated into the present application by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to artificial fusion implants to beplaced into the intervertebral space left remaining after the removal ofa damaged spinal disc and specifically to the apparatus for and methodof, inserting the implants.

[0004] 2. Description of the Prior Art

[0005] For the purpose of achieving long term stability to a segment ofinjured spine, a fusion (the joining together of two or more bones via acontinuous bridge of incorporated bone) may be performed. Well-known tothose skilled in such art is the interbody fusion wherein the disc ispartially excised and bone placed within that space previously occupiedby that disc material (between adjacent vertebrae) for the purpose ofrestoring a more normal spatial relationship, and to provide forstability; short term by mechanical support, and long term by thepermanent cross bonding of bone from vertebra to vertebra. For fusion tooccur within the disc space, it is necessary to prepare the vertebrae tobe fused by breaking through, or cutting into, the hardened outsideplates of bone (the endplates) to allow the interposed bone graft tocome into direct contact with the more vascular cancellous (spongy)bone, and to thereby trick the body into attempting to heal thisinduced, but controlled, “fracturing” by both bone production and thehealing of the grafts to both opposed vertebral surfaces such that theybecome one continuous segment of bone.

[0006] The purpose of the present invention is to provide an implant,and the apparatus and method of inserting the implant within theintervertebral space left after the removal of the disc material andpermanently eliminate all motion at that location. To do so, the deviceof the present invention is space occupying within the disc interspace,rigid, self-stabilizing to resist dislodgement, stabilizing to theadjacent spinal vertebrae to eliminate local motion, and able tointrinsically participate in a vertebra to vertebra bony fusion so as toassure the permanency of the result.

[0007] At present, following the removal of a damaged disc, either boneor nothing is placed into the remaining space. Placing nothing into thisspace allows the space to collapse which may result in damage to thenerves; or the space may fill with scar tissue and eventually lead to areherniation. The use of bone to fill the space is less than optimal inthat bone obtained from the patient requires additional surgery and isof limited availability in its most useful form, and if obtainedelsewhere, lacks living bone cells, carries a significant risk ofinfection, and is also limited in supply as it is usually obtained fromaccident victims. Furthermore, regardless of the source of the bone, itis only marginal structurally and lacks a means to either stabilizeitself against dislodgement, or to stabilize the adjacent vertebrae.

[0008] a. Prior Art Implants

[0009] There have been an extensive number of attempts to develop anacceptable disc prosthesis (an artificial disc). Such devices by designwould be used to replace a damaged disc and seek to restore the heightof the interspace and to restore the normal motion of that spinal joint.No such device has been found that is medically acceptable. This groupof prosthetic or artificial disc replacements, seeking to preservespinal motion and so are different from the present invention, wouldinclude:

[0010] U.S. Pat. No. 3,867,728 to STUBSTAD—describing a flexible discimplant.

[0011] U.S. Pat. No. 4,349,921 to KUNTZ—describing a flexible discreplacement with file-like surface projections to discourage devicedislocation.

[0012] U.S. Pat. No. 4,309,777 to PATIL—describing a motion preservingimplant with spiked outer surfaces to resist dislocation and containinga series of springs to urge the vertebrae away from each other.

[0013] U.S. Pat. No. 3,875,595 to FRONING—describing a motion preservingbladder-like disc replacement with two opposed stud-like projections toresist dislocation.

[0014] U.S. Pat. No. 2,372,622 to FASSIO (France)—describing a motionpreserving implant comprising complimentary opposed convex and concavesurfaces.

[0015] In summary, these devices resemble the present invention only inthat they are placed within the intervertebral space following theremoval of a damaged disc. In that they seek to preserve spinal motion,they are diametrically different from the present invention which seeksto permanently eliminate all motion at that spinal segment.

[0016] A second related area of prior art includes those devicesutilized to replace essentially wholly removed vertebrae. Such removalis generally necessitated by extensive vertebral fractures, or tumors,and is not associated with the treatment of disc disease. While thepresent invention is to be placed within the disc space, these othervertebral devices cannot be placed within the disc space as at least onevertebra has already been removed such that there no longer remains a“disc space”. Furthermore, these devices are limited in that they seekto perform as temporary structural members mechanically replacing theremoved vertebrae (not a removed disc), and do not intrinsicallyparticipate in supplying osteogenic material to achieve cross vertebraebony fusion. Therefore, unlike the present invention which provides fora source of osteogenes is, use of this group of devices must beaccompanied by a further surgery consisting of a bone fusion procedureutilizing conventional technique. This group consisting of vertebralstruts rather than disc replacements would include the following:

[0017] U.S. Pat. No. 4,553,273 to WU—describing a turnbuckle-likevertebral strut.

[0018] U.S. Pat. No. 4,401,112 to REZAIAN—describing a turnbuckle—likevertebral strut with the addition of a long stabilizing staple thatspans the missing vertebral body.

[0019] U.S. Pat. No. 4,554,914 to KAPP—describing a large distractiblespike that elongates with a screw mechanism to span the gap left by theremoval of an entire vertebra and to serve as an anchor for acryliccement which is then used to replace the missing bone (vertebrae).

[0020] U.S. Pat. No. 4,636,217 to OGILVIE—describing a vertebral strutmechanism that can be implanted after at least one vertebrae has beenremoved and consists of a mechanism for causing the engagement of screwsinto the vertebrae above and the vertebrae below the one removed.

[0021] In summary, this second group of devices differs from the presentinvention in that they are vertebral replacements struts, do notintrinsically participate in the bony fusion, can only be inserted inthe limited circumstances where an entire vertebra has been removed fromthe anterior approach, and are not designed for, or intended to be usedfor the treatment of disc disease.

[0022] A third area of prior art related to the present inventionincludes all devices designed to be applied to one of the surfaces ofthe spine. Such devices include all types of plates, struts, and rodswhich are attached by hooks, wires and screws. These devices differsignificantly from the present invention in that they are not insertedwithin the disc space and furthermore do not intrinsically participatein supplying osteogenic material for the fusion.

[0023] Therefore, where permanent spinal immobilization is desired, anadditional surgery, consisting of a spinal fusion performed byconventional means or the use of supplemental methylmethacrylate cementis required. Such devices applied to the spine, but not within the discspace, would include the following:

[0024] U.S. Pat. No. 4,604,995 to STEPHENS—describing a “U” shaped metalrod attached to the posterior elements of the spine with wires tostabilize the spine over a large number of segments.

[0025] U.S. Pat. No. 2,677,369 to KNOWLES—describing a metal columndevice to be placed posteriorly along the lumbar spine to be held inposition by its shape alone and to block pressure across the posteriorportions of the spinal column by locking the spine in full flexionthereby shifting the maximum weight back onto the patient's own disc.

[0026] Other devices are simply variations on the use of rods (e.g.Harringtgn, Luque, Cotrel-Dubosset, Zielke), wires or cables (Dwyer),plates and screws (Steffee), or struts (Dunn, Knowles) In summary, noneof these devices are designed to be nor can be used within the discspace. Moreover, these devices do not replace a damaged disc, and do notintrinsically participate in the generation of a bony fusion.

[0027] Another area of related prior art to be considered is that ofdevices designed to be placed within the vertebral interspace followingthe removal of a damaged disc, and seeking to eliminate further motionat that location.

[0028] Such a device is contained in U.S. Pat. No. 4,501,269 issued toBAGBY which describes an implantable device and limited instrumentation.The method employed is as follows: a hole is bored transversely acrossthe joint and a hollow metal basket of larger diameter than the hole isthen pounded into the hole and then the hollow metal basket is filledwith the bone debris generated by the drilling.

[0029] While the present invention (device, instrumentation, and method)may appear to bear some superficial resemblance to the BAGEY invention,it is minimal, while the differences are many fold and highlysignificant. These differences include the following:

[0030] 1. Safety—The present invention provides for a system ofcompletely guarded instrumentation so that all contiguous vitalstructures (e.g. large blood vessels, neural structures) are absolutelyprotected. The instrumentation of the present invention also makesoverpenetration by the drill impossible. Such overpenetration in thecervical spine, for example, would result in the total paralysis ordeath of the patient. In the thoracic spine, the result would becomplete paraplegia. In the lumbar spine, the result would be paraplegiaor a life-threatening perforation of the aorta, vena cava, or iliacvessels.

[0031] The present invention is atraumatically screwed into place whilethe BAGBY device, in contradistinction, is pounded into position. BAGBYdescribes that its implant is significantly larger in size than the holedrilled and must be pounded in. This is extremely dangerous and thepounding occurs directly over the spinal cord which is precariouslyvulnerable to percussive injury. Furthermore, while it is possible, forexample in the lumbar spine, to insert the present invention away fromthe spinal cord and nerves, the BAGBY device must always be poundeddirectly towards the spinal cord.

[0032] Furthermore, since the BAGBY device is pounded into a smooth holeunder great resistance, and lacking any specific design features tosecure it, the device is highly susceptible to forceful ejection whichwould result in great danger to the patient and clinical failure. Thepresent invention, in contradistinction, is securely screwed into place,and possesses highly specialized locking threads to make accidentaldislodgement impossible. Because of the proximity of the spinal cord,spinal nerves, and blood vessels, any implant dislodgement as mightoccur with the BAGBY device might have catastrophic consequences.

[0033] 2. Broad applicability—The BAGBY device can only be inserted fromthe front of the vertebral column, however, in contrast, the presentinvention can be utilized in the cervical, thoracic, and lumbar spine,and can be inserted from behind (posteriorly) in the lumbar spine. Thisis of great importance in that the purpose of these devices is in thetreatment of disc disease and probably greater than 99 percent of alllumbar operations for the treatment of disc disease are performed frombehind where the present invention can easily be utilized, but the BAGBYdevice, as per BAGBY'S description, cannot.

[0034] 3. Disc removal—The BAGBY invention requires the complete removalof the disc prior to the drilling step, whereas the present inventioneliminates the laborious separate process of disc removal andefficiently removes the disc and prepares the vertebral end plates in asingle step.

[0035] 4. Time required—The present invention saves time over the BAGBYinvention since time is not wasted laboring to remove the disc prior toinitiating the fusion. Also, with the present invention the procedure isperformed through a system of guarded instrumentation, time is notwasted constantly placing and replacing various soft tissue retractorsthroughout the procedure.

[0036] 5. Implant stability—Dislodgement of the implant would be a majorsource of device failure (an unsuccessful clinical result), and mightresult in patient paralysis or even death. As discussed, the BAGBYdevice lacks any specific means of achieving stability and since it ispounded in against resistance to achieve vertebral distraction, and issusceptible to forceful dislodgement by the tendency of the twodistracted vertebrae, to return to their original positions squeezingout the device. The present invention, however, is screwed into place.As there is no unscrewing force present between the vertebrae,compression alone cannot dislodge the implant. The implant is inherentlystable by its design. Furthermore, the threads of the present inventionare highly specialized in that they are periodically interrupted so thatthe tail ends of each of the tabs so formed are blunted and twisted soas to resist accidental unscrewing. The removal of an implant with such“locking threads” requires the use of a special extractor includedwithin the instrumentation. The stability of the present invention isstill further enhanced, again in contradistinction to the BAGBY device,by the presence of a “bone ingrowth” surface texturing, which bothincreases the friction of the fit and allows for the direct growth ofthe vertebral bone into the casing of the implant itself.

[0037] 6. Soinal stability—The present invention is not onlyself-stabilizing, it also provides stability to the adjacent vertebraein at least three ways that the BAGBY device cannot. First, the BAGBYdevice is placed transversely across the joint in the center, leavingboth vertebrae free to rock back and forth over this round barrel shapedaxis, much like a board over a barrel, being used for a seesaw.

[0038] Secondly, as the BAGBY device lacks any specific design featuresto resist sliding, it may actually behave as a third body allowing thetranslation of the vertebrae relative to the device and to each other.

[0039] Thirdly, any device can only provide stability if it remainsproperly, seated. The present invention is inherently stable, andtherefore assures that it will stabilize the adjacent vertebrae, ratherthan, as with the BAGBY, the instability of the spine to be treated maycause a dislocation of the BAGBY implant, with further loss of spinalstability.

[0040] 7. The collapse of the interspace—While both the presentinvention and the BAGBY device can be fabricated to withstand thecompression forces within the interspace, the interspace maynevertheless collapse under the superincumbent body weight as theimplant settles into the vertebral bone. This is related to the load perunit area. Again the present invention is superior to the BAGBY devicein at least four ways.

[0041] First, the present invention offers considerably greater surfacearea to distribute the load. Secondly, while the BAGBY device is placedcentrally, the present device is placed bilaterally where the bone tendsto be more cortical and much stronger out towards the rim. Thirdly, thepresent invention supports the load achieving an “I” beam effect,whereas the BAGBY implant does not. Fourthly, it is not pressure alonethat causes the collapse of the bone adjacent to the implant, but alsobony erosion that is caused by the motion under pressure of the implantagainst the bone. As discussed in item 6 above, the present inventionalone is highly resistant to such motion, again diminishing thelikelihood of erosion and interspace collapse.

[0042] 8. Bone ingrowth surface texturing—The present invention has asurface treatment of known and conventional technology to induce thegrowth of bone from the vertebrae directly into the casing material ofthe implant itself. The BAGBY device has no similar feature. {L.A.—wemay want to list examples of these bone growth factors}

[0043] 9. Fusion mass—The BAGBY invention calls for removing the discand then drilling a hole between the adjacent vertebrae. The bony debrisso generated is then put into the device. The present invention takes acore of pure bone producing marrow from the iliac crest, and then by useof a special press, forcibly injects the implant device with anextremely dense compressed core of that osteogenic material until thematerial itself virtually extrudes from every cell of the implant.

[0044] 10. The probability of achieving fusion—The fusion rate withinthe spine is known to be related directly to the amount of exposedvascular bone bed area, the quality and quantity of the fusion massavailable, and the extent of the stabilization obtained with all otherfactors being half constant. It would then be anticipated, that thefusion rate would be superior with the present invention as compared tothe BAGBY device, because of optimal implant stability (#5), optimalspinal stability (#6), bone ingrowth surface treatment (#8), superiorfusion mass (#9), and the greater exposed vertebral bony surface area(#7).

[0045] The last area of prior art possibly related to the presentinvention and therefore, to be considered related to “bony ingrowth”,are patents that either describe methods of producing materials and ormaterials or devices to achieve the same. Such patents would include:

[0046] U.S. Pat. Nos. 4,636,526 (DORMAN), 4,634,720 (DORMAN), 4,542,539(ROWE), 4,405,319 (COSENTINO), 4,439,152 (SMALL), 4,168,326 (BROEMER),4,535,485 (ASILAN), 3,987,499 (SC ARBACH), 3,605,123 (HAHN), 4,655,777(DUNN), 4,645,503 (LIN), 4,547,390 (ASHMAN), 4,608,052 (VAN KAMPEN),4,698,375 (DORMAN), 4,661,536 (DORMAN), 3,952,334 (BOKROS), 3,905,047(LONG), 4,693,721 (DUCHEYNE), 4,070,514 (ENTHERLY).

[0047] However, while the implant of the present invention would utilizebone ingrowth technology, it would do so with conventional technology.

[0048] b. Prior Art Instrumentations And Methods

[0049] The following is a history of the prior art apparatus and methodsof inserting spinal implants:

[0050] In 1956, Ralph Cloward developed a method and instruments whichhe later described for preparing the anterior aspect (front) of thecervical spine, and then fusing it. Cloward surgically removed the discto be fused across and then placed a rigid drill guide with a large footplate and prongs down over an aligner rod and embedded said prongs intothe adjacent vertebrae to maintain the alignment so as to facilitate thereaming out of the bone adjacent the disc spaces. As the large footplate sat against the front of the spine, it also served as a fixedreference point to control the depth of drilling. The reaming left twoopposed resected arcs, one each, from the opposed vertebral surfaces.The tubular drill guide, which was placed only preliminary to thedrilling, was thereafter completely removed. A cylindrical bony dowel,significantly larger in diameter than the hole formed, was then poundedinto the hole already drilled. Cloward's method of instrumentation wasdesigned for, and limited to, use on the anterior aspect and in theregion of the cervical spine only. The hole was midline, which wouldpreclude its use posteriorly where the spinal cord would be in the way.

[0051] As the bone graft to be inserted in Cloward's method wasnecessarily larger in diameter than the hole drilled, the graft couldnot be inserted through the drill guide. This mandated the removal ofthe drill guide and left the graft insertion phase completelyunprotected. Thus Cloward's method and instrumentation was inappropriatefor posterior application.

[0052] In addition, the failure to provide continuous protection to thedelicate neural structures from the instruments, as well as the bony andcartilaginous debris generated during the procedure, made Cloward'smethod inappropriate for posterior application. Also, the drill guidedescribed by Cloward could not be placed posteriorly within the spinalcanal, as the foot plate would crush the nerves. Modifying Cloward'sdrill guide by removing the foot plate completely, would still leave theinstrument unworkable as it would then lack stability, and would not becontrollable for depth of seating.

[0053] Nevertheless, Wilterberger, (Wilterberger, B. R., Abbott, K. H.,“Dowel Intervertebral Fusion as Used in Lumbar Disc Surgery,” TheJournal of Bone and Joint Surgery, Volume 39A, pg. 234-292, 1957)described the unprotected drilling of a hole from the posterior into thelumbar spine between the nerve roots and across the disc space, and theninserting a stack of button-like dowels into that space. WhileWilterberger had taken the Cloward concept of circular drilling anddowel fusion and applied it to the lumbar spine from a posteriorapproach, he had not provided for an improved method, nor had headvanced the instrumentation so as to make that procedure sufficientlysafe, and it rapidly fell into disrepute.

[0054] Crock (Crock, H. V., “Anterior Lumbar Interbody FusionIndications for its Use and notes on Surgical Technique,” ClinicalOrthopedics, Volume 165, pg. 157-163, 1981) described his technique andinstrumentation for Anterior Interbody Fusion of the lumbar spine,wherein he drilled two large holes side by side across the disc spacefrom anterior to posterior essentially unprotected and then pounded intwo at least partially cylindrical grafts larger than the holesprepared.

[0055] A review of the prior art is instructive as to a number ofsignificant deficiencies in regard to the method and instrumentation forthe performance of Interbody Spinal Fusion utilizing drilling to preparethe endplates.

[0056] As the great majority of spinal surgery is performed in thelumbar spine and from posteriorly, a review of the prior art reveals anumber of deficiencies in regard to the spine in general, and to theposterior approach to the lumbar spine specifically. These deficienciesinclude the:

[0057] 1. Failure to protect the surrounding tissues throughout theprocedure, specifically, prior to drilling and until after the insertionof the graft;

[0058] 2. Failure to contain the debris, bony and cartilaginous,generated during the procedure;

[0059] 3. Failure to optimize the contact of the cylindrical drill holeand bone graft, the mismatch in their diameters resulting inincongruence of fit;

[0060] 4. Failure to determine the optimal drill size prior to drilling;

[0061] 5. Failure to determine the optimal amount of distraction priorto drilling;

[0062] 6. Inability to optimize the amount of distraction so as torestore the normal spatial relationships between adjacent vertebrae;

[0063] 7. Inability to create sufficient working space within the spinalcanal (between the nerve roots and the dural sac) to make the proceduresafe;

[0064] 8. Absent a foot plate on the drill guide, as necessitated by theclose tolerances posteriorly, the inability to reliably insure that thedrilling is parallel to the vertebral endplates;

[0065] 9. The inability to insure equal bone removal from the opposedvertebral surfaces; and

[0066] 10. The inability to determine within the spinal canal, theproper side by side positioning for dual drill holes.

BRIEF SUMMARY OF THE INVENTION

[0067] The present invention comprises a series of artificial implants,the purpose of which is to participate in, and directly cause bonefusion across an intervertebral space following the excision of adamaged disc. Such implants are structurally load bearing devices,stronger than bone, capable of withstanding the substantial forcesgenerated within the spinal interspace. The devices of the presentinvention have a plurality of macro sized cells and openings, which canbe loaded with fusion promoting materials, such as autogenous bone, forthe purpose of materially influencing the adjacent vertebrae to performa bony bond to the implants and to each other. The implant casing may besurface textured or otherwise treated by any of a number of knowntechnologies to achieve a “bone ingrowth surface” to further enhance thestability of the implant and to expedite the fusion.

[0068] The devices of the present invention are configured and designedso as to promote their own stability within the vertebral interspace andto resist being dislodged, and furthermore, to stabilize the adjacentspinal segments.

[0069] The apparatus and method of the present invention for preparingthe vertebrae for insertion of the implant allows for the rapid and saferemoval of the disc, preparation of the vertebrae, performance of thefusion, and internal stabilization of the spinal segment.

[0070] The present invention is a method for Interbody Spinal Fusionutilizing novel instrumentation, whereby a protective tubular member, orpaired tubular members are placed prior to the drilling part of theprocedure and may be left in place until the implant is fully seated.

[0071] By way of example, regarding the posterior approach to the lumbarspine, two distractors are used to separate two adjacent vertebrae to apreferred distance. A hollow Outer Sleeve having teeth at one end isdriven into the adjacent vertebrae on one side to hold the vertebrae inposition when the distractor is removed, a diameter reducing hollowInner Sleeve is introduced into the Outer Sleeve, a drill having a drillstop is passed through the hollow Inner Sleeve to drill a hole to adesired depth, and an implant is inserted in the hole. The method isrepeated on the other side of the disc.

[0072] The present invention provides apparatus and method of insertingspinal implants from the anterior, posterior and lateral aspect of thespine. The instrumentation and method of the present invention providesa distractor instrument configured to restore and maintain the normalangular relationship of the vertebrae of the spine, known as lordosis orkyphosis, prior to the completion of the fusion procedure. The presentinvention also provides an extended outer sleeve that is a combinationdistractor and outer sleeve used for performing the surgical procedureof the present invention. The combination distractor and outer sleevemay also be configured to maintain the normal angular relationship ofthe vertebrae during the surgical procedure. The present inventionfurther discloses a combination distractor outer sleeve that may be usedto perform the surgical procedure of the present invention from thelateral aspect of the spinal column that protects the great vessels andneural structures from being damaged during the surgical procedure.

[0073] In summary then, the present invention, instrumentation, andmethod, provides for the performance of a total nuclear discectomy, aninterbody fusion, a rigid internal fixation of the spine as a singleintegrated surgical procedure.

[0074] Discussion of the Instrumentation

[0075] The apparatus and method of the present invention provide thefollowing advantages:

[0076] 1. The present invention is safer by providing protection of thesurrounding tissues. An Outer Sleeve places all of the delicate softtissue structures, nerves, blood vessels, and organs outside of the pathof the various sharp surgical instruments and the implant. Further, itis an improvement upon hand held retractors in that it occupies theleast possible amount of area, avoids the stretching associated withmanual retraction, provides for the retraction and shielding of thesurrounding tissues in all directions circumferentially andsimultaneously, and it does so exclusively with smooth, curved surfaces.

[0077] 2. The present invention is safer by providing protection againstthe danger of instrument or implant overpenetration.

[0078] 3. The present invention is safer as the surgical site and woundare protected from the debris generated during the procedure.

[0079] 4. The present invention is safer because the method provides forabsolute protection to the soft tissues directly and from indirectinjury by overpenetration. It makes safe the use of powerinstrumentation which is both more effective and efficient.

[0080] 5. The present invention maintains the vertebrae to be fusedrigid throughout the procedure.

[0081] 6. The present invention holds the vertebrae to be fused alignedthroughout the procedure.

[0082] 7. The present invention holds the vertebrae to be fuseddistracted throughout the procedure.

[0083] 8. The present invention assures that all instruments introducedthrough the Outer Sleeve are coaxial and equally centered through thedisc space and parallel the endplates.

[0084] 9. The present invention facilitates the implant insertion bycountering the high compressive forces tending to collapse theinterspace, which if left unchecked would resist the introduction andadvancement of the implant and make stripping more likely.

[0085] 10. The present invention extends the range and use of theprocedure and similarly the interbody spinal implant itself by makingthe procedure safe throughout the spine.

[0086] 11. The present invention increases the ability to use aspecifically sized implant.

[0087] 12. In the present invention the end of all the penetratinginstrumentation is blunt faced.

[0088] 13. In the present invention all of the instruments have beenstopped at a predetermined depth to avoid overpenetration.

[0089] 14. The design of the Outer Sleeve in the present inventionconforms to the spacial limitations of the specific surgical site.

[0090] 15. The design and use of a second or Inner Sleeve in the presentinvention allows for the difference in size between the inside diameterof the Outer Sleeve, and the outside diameter of the drill itself. Thisdifference being necessary to accommodate the sum of the distraction tobe produced, and the depth of the circumferential threading present ofthe implant.

[0091] 16. In the present invention a specially designed drill bit witha central shaft recess allows for the safe collection of the drillingproducts, which can then be removed without disturbing the Outer Sleeveby removing the drill bit and Inner Sleeve as a single unit.

[0092] 17. In the present invention a specially designed trephine isprovided for preparing cylindrical holes across the disc space and intotwo adjacent vertebrae, and for harvesting of the bone graft by removinga core of bone slightly smaller in diameter than the internal diameterof the implant cavity itself, however of a greater length.

[0093] 18. In the present invention a specially designed press forforcefully compressing and injecting the long core of autogenous boneinto the implant, such that it extrudes through the implant itself.

[0094] 19. In the present invention a specially designed driverextractor, which attaches to the implant and allows the implant to beeither inserted or removed without itself dissociating from the implant,except by the deliberate disengagement of the operator.

[0095] 20. In the present invention predistraction increases the workingspace.

[0096] 21. The Distractor in the present invention is self-orientingacting as a directional finder.

[0097] 22. The Distractor in the present invention is self-centralizingbetween the opposed vertebral surfaces acting as a centering post forthe subsequent bone removal.

[0098] 23. In the present invention predistraction assures the equalremoval of bone from the adjacent vertebral surfaces.

[0099] 24. In the present invention predistraction assures the exactcongruence between the hole drilled and the device.

[0100] 25. In the present invention predistraction assures that thedrilling is parallel to the vertebral endplates.

[0101] 26. In the present invention predistraction allows for thedetermination of the optimal distraction prior to drilling.

[0102] 27. In the present invention predistraction allows for theverification of the correct prosthesis size prior to drilling.

[0103] 28. In the present invention predistraction facilitates deviceinsertion by relieving the compressive loads across the interspace whichwould resist implantation.

[0104] 29. In the present invention predistraction decreases thelikelihood of stripping the bone during insertion.

[0105] 30. In the present invention predistraction provides for the sideby side positioning, spacing, and parallelism required prior to theirrevocable event of drilling.

[0106] 31. In the present invention predistraction provides for therigid stabilization of the vertebrae opposed to the disc spacethroughout the surgical procedure.

[0107] 32. In the present invention predistraction provides for animplant easier to insert as the compressive loads of the opposedvertebrae are held in check so that the device itself need not drive thevertebrae apart to be inserted.

[0108] 33. In the present invention predistraction allows for theinsertion of a more effective implant as more of the implant can bededicated to its intended purpose and be full diameter, whereas withoutthe benefit of predistraction and the ability to maintain the same, asignificant portion of the forward end of the implant would need to bededicated to the purpose of separating the opposing vertebrae.

[0109] 34. The present invention allows for the use of an implant with asharper thread or surface projections as there is no danger to thesurrounding tissues.

[0110] 35. The present invention allows for the implant to be fullypreloaded as provided to the surgeon, or for the surgeon to load it withthe material of his choice at the time of surgery.

[0111] 36. The present invention allows for the loading of a spinalimplant outside of the spinal canal and prior to implantation.

[0112] 37. The present invention provides for Distractors for therestoration of the physiologic amount of lordosis/kyphosis at any givenlevel of the spine.

[0113] 38. The Distractors of the present invention provide for therestoration of sagittal spinal alignment and the segmental correction ofscoliosis.

[0114] 39. The present invention provides Extended Outer Sleeves whichare a combined Distractor and Outer Sleeve for the three dimensionalsegmental restoration of spinal alignment.

OBJECTS OF THE PRESENT INVENTION

[0115] It is an object of the present invention to provide an improvedmethod of performing a discectomy, a fusion, and an internalstabilization of the spine, and specifically, all three of the abovesimultaneously and as a single procedure.

[0116] It is another object of the present invention to provide animproved method of performing a discectomy, a fusion, and an internalstabilization of the spine, which is both quicker and safer than ispossible by previous methods.

[0117] It is another object of the present invention to provide animproved method of performing a discectomy, a fusion and an internalstabilization of the spine, to provide for improved surgical spinalimplants.

[0118] It is another object of the present invention to provide animproved method of performing a discectomy, a fusion, and an internalstabilization of the spine, which provides for an improved system ofsurgical instrumentation to facilitate the performance of the combineddiscectomy, fusion, and internal spinal stabilization.

[0119] It is another object of the present invention to provide animproved method of performing a discectomy, a fusion, and an internalstabilization of the spine.

[0120] It is an object of the present invention to provideinstrumentation and a method of spinal interbody arthrodesis that isfaster, safer, and more efficacious than prior methods, and caneffectively be performed in the cervical, thoracic, and lumbar spineanteriorly, as well as in the lower lumbar spine posteriorly.

[0121] It is a further object of the present invention to provide ameans for inserting a spinal implant between adjacent vertebrae whilemaintaining their optimal spacing, positioning, and alignment.

[0122] It is another object of the present invention to provideinstrumentation for restoring and maintaining the normal angularrelationship of adjacent vertebrae of the spine, be it lordosis,kyphosis, and/or the segmental correction of scoliosis, achieving atotal nuclear discectomy, an interbody spinal fusion, and a rigidinternal fixation of a segment of the spine as a single integratedsurgical procedure for spinal fusion.

[0123] It is another object of the present invention to provide for aninstrument that is a combination Outer Sleeve and Distractor forinserting a spinal implant between adjacent vertebrae while effectingand maintaining the optimal, spacing, positioning, and alignment of thevertebrae.

[0124] It is another object of the present invention to provide aDistractor capable of restoring and maintaining the normal angularrelationship between adjacent vertebrae that may be inserted within thedisc space between two adjacent vertebrae.

[0125] It is yet another object of the present invention to provideinstrumentation and a method of spinal interbody arthrodesis that isfaster, safer, and more efficacious than prior methods, and caneffectively be performed in the cervical, thoracic, and lumbar spine.

[0126] These and other objects of the present invention will be apparentfrom review of the following specification and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0127]FIG. 1 is a side elevational view of the Long Distractor, of thepresent invention inserted into the intervertebral space.

[0128]FIG. 2 is a side elevational view of a Convertible Distractorassembly in relation to the spine.

[0129]FIG. 3 is a perspective view of a high retention Short Distractorof FIG. 2.

[0130]FIG. 3A is a side elevational view of the high retention ShortDistractor of FIG. 3.

[0131]FIG. 3B is a side elevational view of an alternative ShortDistractor with circumferential forward facing ratchetings.

[0132]FIG. 3C is a top view of the alternative Short Distractor of FIG.3B.

[0133]FIG. 3D is a perspective view of an alternative embodiment of aShort Distractor.

[0134]FIG. 3E is a top view of the alternative distractor of FIG. 3D.

[0135]FIG. 3F is a side elevational view of a further alternativerectangularized Short Distractor with knurled surfaces.

[0136]FIG. 4 is a perspective view of a spinal segment (two vertebraeand an interposed disc) with a Short Distractor in place, with a portionof the upper vertebrae and disc cut away to show the Short Distractor onone side of the spine and the Long Distractor about to be placedcontralaterally.

[0137]FIG. 5 is a side elevational view of the Outer Sleeve in placeover the Long Distractor, and about to receive the Driver Cap inpreparation for being seated.

[0138]FIG. 6 is a side elevational view of the Long Distractor, OuterSleeve, and Driver Cap following the proper seating of the Outer Sleeveinto the two adjacent vertebrae.

[0139]FIG. 7A is a side elevational view of the cervical Outer Sleevebeing placed over a Long Distractor which is in place within the discspace anteriorly.

[0140]FIG. 7B is a bottom plan view of the single Outer Sleeve of FIG.7A.

[0141]FIG. 7C is a bottom plan view of a Dual Outer Sleeve.

[0142]FIG. 7D is a side elevational view of the proximal portion of FIG.7C.

[0143]FIG. 7E is a bottom plan view of a Dual Driver Cap for driving twodistractors.

[0144]FIG. 7F is a side sectional view showing the Dual Outer Sleeve ofFIGS. 7C and 7D, Distractors and Dual Cap of FIG. 7E seated in relationto the vertebrae.

[0145]FIG. 8 is a side elevational view of the Outer Sleeve of FIG. 7Acentered on the Long Distractor and fully seated on the anterior aspectof the cervical spine.

[0146]FIG. 9 is a perspective side view of the Distractor Puller.

[0147]FIG. 10 is a side elevational view of the Proximal Puller engagingthe extraction ring of the Long Distractor shown in hidden line over theend of the Outer Sleeve.

[0148]FIG. 10A is a partial side elevational view of the Proximal Pullercoupled to the Long Distractor just prior to its extraction.

[0149]FIG. 10B is a posterior view of the proximal Outer Sleeve and aShort Distractor shown in hidden line in place in regard to thevertebrae, disc and nerves.

[0150]FIG. 11A is a side sectional view of the Drill and Inner Sleevewithin the Outer Sleeve drilling across the intervertebral space andcutting partially cylindrical arcs from the adjacent vertebrae.

[0151]FIG. 11B is a side elevational view of preparation of theintervertebral space by the alternative “Trephine Method” showing theDistractor, Trephine, Inner Sleeve, and Outer Sleeve in place.

[0152]FIG. 11C is a side elevational view as in FIG. 11A, but showingthe use of an alternative drilling conformation wherein the extendedproximal portion of the Drill is both distracting and self-centering.

[0153]FIG. 11D is a side perspective view of an instrument for removingarcs of bone from vertebrae following drilling.

[0154]FIG. 12 is a side perspective view of the surgical Tap.

[0155]FIG. 13 is a partial sectional side view of the Outer Sleeve andthe surgical Tap fully threaded within the interspace.

[0156]FIG. 14A is a side elevational view of the bone harvestingTrephine and motor adapter.

[0157]FIG. 14B is a perspective side view of the implant Bone LoadingDevice.

[0158]FIG. 14C is a perspective side view of the Corkscrew bone freeingand extracting instrument.

[0159]FIG. 15 is a perspective side view of the Bone Loading Device inoperation.

[0160]FIG. 16 is a partial sectional perspective side view of theImplant Driver about to engage the spinal implant.

[0161]FIG. 17 is a partial sectional side elevational view of the spinalimplant being fully seated within the intervertebral space by means ofthe Driver apparatus in place within the Outer Sleeve.

[0162]FIG. 18 is a side elevational view of the lumbar spine showing theend result of the spinal implant implantation via the posterior route.

[0163]FIG. 19 is a side elevational view of a Posterior Long LordoticDistractor inserted from the posterior aspect of the spine betweenadjacent vertebrae to restore and maintain lordosis of the spine.

[0164]FIG. 20 is a side elevational view of the Posterior Long LordoticDistractor shown partially in hidden line with the Outer Sleeve and Cap,inserted between adjacent vertebrae to restore and maintain lordosis ofthe spine with the Outer Sleeve engaging the vertebrae and properlyseated over the Posterior Long Lordotic Distractor.

[0165]FIG. 21 is a side elevational view partially in cross section of aspinal implant being inserted through an Outer Sleeve between twoadjacent vertebrae of the spine in which lordosis has been restored andmaintained and in which a portion of bone has been removed from eachvertebrae for receiving the spinal fusion implant.

[0166]FIG. 22 is a side elevational view of a spinal implant insertedbetween two adjacent vertebrae of the spine in which lordosis has beenrestored.

[0167]FIG. 23 is a side elevational view of a Posterior Short LordoticDistractor of the present invention.

[0168]FIG. 24 is a top plan view along lines 24—24 of FIG. 23 of thePosterior Short Lordotic Distractor of the present invention.

[0169]FIG. 25 is a side elevational view of an Anterior Long LordoticDistractor of the present invention shown inserted between two adjacentvertebrae from the anterior aspect of the spine to restore and maintainlordosis.

[0170]FIG. 26 is a perspective side view of the Extended Outer Sleeve ofthe present invention having extended members for insertion within thedisc space and engaging means for engaging adjacent vertebrae of thespine.

[0171]FIG. 27 is a side elevational view of the Extended Outer Sleeve ofFIG. 26 shown inserted between adjacent vertebrae of the spine.

[0172]FIG. 28 is an alternative embodiment of the Extended Outer Sleeveof FIG. 26 shown without an engaging means for engaging adjacentvertebrae.

[0173]FIG. 29 is a perspective side view of a Posterior LordoticExtended Outer Sleeve of the present invention having uneven extendedmembers for restoring and maintaining lordosis of the spine andengagement means for engaging the vertebrae.

[0174]FIG. 30 is a side elevational view of a portion of the PosteriorLordotic Extended Outer Sleeve of FIG. 29 inserted between adjacentvertebrae from the posterior aspect of the spine to restore and maintainlordosis.

[0175]FIG. 31 is a perspective side view of an Anterior LordoticExtended Outer Sleeve of the present invention having extended membersfor restoring and maintaining lordosis of the spine from the anterioraspect of the spine.

[0176]FIG. 32 is a side elevational side view of an alternativeembodiment of the Anterior Lordotic Extended Outer Sleeve of FIG. 31absent the engagement means for engaging the vertebrae, inserted betweenadjacent vertebrae from the anterior aspect of the spine.

[0177]FIG. 33 is a perspective side view of a Dual Extended Outer Sleevehaving an uneven extended portion which decreases in height in thedirection of insertion.

[0178]FIG. 34 is bottom plan view of the foot plate of the Dual ExtendedOuter Sleeve of FIG. 33.

[0179]FIG. 35 is a perspective side view of a Dual Extended Outer Sleevehaving uneven extended portions which decrease in height in thedirection insertion.

[0180]FIG. 36 is an elevational front view of the apparatus of thepresent invention for use in installing interbody spinal implants havingone or more flat sides, shown placed over two Long Distractors with theprongs inserted into the vertebrae.

[0181]FIG. 37 is a bottom plan view of the foot plate of the apparatusof the present invention for use in installing the interbody spinalimplants having one or more flat sides.

[0182]FIG. 38 is a cross sectional view along line 38—38 of FIG. 36illustrating the apparatus used for inserting interbody spinal implantshaving one or more flat sides.

[0183]FIG. 39 is a partial fragmentary view of the apparatus of thepresent invention for use in installing interbody spinal implants havingone or more flat sides, shown with the prongs being partially insertedinto the vertebrae.

[0184]FIG. 40 illustrates a step of the method of drilling a hole into avertebrae with the apparatus of the present invention for use ininstalling interbody spinal implants having one or more flat sides,shown engaged to two adjacent vertebrae of a spinal column.

[0185]FIG. 41 illustrates a step of the method of the present inventionfor inserting a second interbody spinal implant having one or more flatsides into the interspace between two adjacent vertebrae with oneimplant shown already installed in place.

DETAILED DESCRIPTION OF THE DRAWINGS AND DETAILED DESCRIPTION OF METHODOF INSERTION

[0186] The following discussion will be in regard to application in thelumbar spine via the posterior approach. In its simplest form, themethod of the present invention involves the following steps. Thepatient is placed on a spinal surgery frame, which allows for thedistraction and alignment of the disc space to be fused. A bilateralposterior exposure of the interspace, with or without partial discectomyis then performed. Utilizing distractors the disc space is distracted,and a hollow Outer Sleeve is fitted over one of the distractors. The endof the Outer Sleeve has engagement means, such as teeth, for engagingthe two adjacent vertebrae. The Outer Sleeve is driven into thevertebrae and the distractor is then removed. A hollow Inner Sleeve isthen inserted into the Outer Sleeve and a stopped Drill is utilized toprepare the opposed vertebral surfaces. The Drill and the Inner Sleeveare removed as a single unit. The space is tapped if so required. Theprepared spinal implant is then inserted via the Outer Sleeve utilizinga stopped inserter. The instruments are then removed and the procedurerepeated on the contralateral side of the spine.

[0187] Detailed Description of the Preferred Embodiment

[0188] Step 1a. Prior to surgery, translucent implant templatesappropriately adjusted for scale are superimposed on AP, lateral, andaxial images of the interspace to be fused, for the purpose of selectingthe optimal implant size and to determine the desired distraction.

[0189] Step 1b. The patient is preferably placed onto a spinal surgeryframe capable of inducing both distraction and vertebral alignment.

[0190] Step 2. In the preferred embodiment, a standard bilateral(partial) discectomy is performed and any posterior lipping of thevertebral bodies adjacent the interspace is removed. Alternatively, nodisc material need be removed. In the preferred embodiment, theinterspace is exposed by performing bilateral pairedsemihemilaminotomies and resecting the inner aspects of the facet jointsadjacent the spinal canal while preserving the supra and interspinousligaments.

[0191] Step 3. Beginning on the first side, the dural sac and traversingnerve root at that level are retracted medially and a Long Distractorthen inserted and impacted flush to the posterior vertebral bodiesadjacent that interspace. Long Distractors with working ends ofincreasing diameter are then sequentially inserted until the optimaldistraction is obtained. This optimal distraction not only restores thenormal height of the interspace, but further achieves a balance whereinthe tendency for the space to collapse is resisted, which in urging thevertebral bodies apart is being equally resisted by the powerful softtissue structures about the spinal segment including the outer casing ofthe disc (the annulus fibrosus), various ligaments, capsular structures,as well as the muscles and other soft tissue structures. This balanceddistraction not only provides for the spatial restoration of the heightof the interspace, but for considerable stability as the space nowresists further distraction or collapse.

[0192] In the preferred embodiment, as the desired distraction isapproached, the use of the solid bodied Long Distractors is terminatedand a disassemblable Convertible Distractor is placed with tactileand/or radiographic confirmation of ideal distraction. The ConvertibleDistractor is then disassembled such that the Short Distractor portionis left in place and the ultra-low profile head portion being positionedadjacent to the canal floor and safely away from the neural structures.To insure that the Short Distractor remains in place until its removalis desired, various embodiments of the Short Distractor are availablewith varying degrees of resistance to dislodgment. In the preferredembodiment of the procedure, attention is then directed to thecontralateral side of the spine.

[0193] Step 4. On the contralateral side of the same interspace the LongDistractor having at its working end the diameter matching the ShortDistractor already in place, is then inserted. If however, due to anasymmetrical collapse of the interspace if it is then determined thatgreater distraction is required on the second side to achieve theoptimal stability, then the appropriate Short Distractor would be placedon the second side. Then the Short Distractor would be removed from thefirst side and replaced with a larger Long Distractor so as to bring theinterspace into balance.

[0194] In an alternative embodiment, the entire procedure is performedon the one side of the spine utilizing only the Long Distractor prior torepeating the procedure on the contralateral side of the spine. Whilethis method can be performed in accordance with the remaining steps asdescribed in the preferred embodiment, when utilized it is bestperformed using a Trephine which allows the Long Distractor to remain inplace, thereby allowing for interspace distraction otherwise provided inthe first method by the Short Distractor. This alternative method thenrequires the use of a Trephine over the Long Distractor in lieu of areamer and is therefore called the “Trephine Method”, which will bediscussed in detail later.

[0195] Step 5. With the Short Distractor in place on the first side ofthe spine, and the matching Long Distractor in place on the second sideof the spine, and with the dural sac and traversing nerve root safelyretracted, the Outer Sleeve is placed over the Long Distractor andfirmly impacted to its optimal depth using the Impaction Cap and amallet. The Long Distractor is then removed.

[0196] Step 6. An Inner Sleeve is then placed within the Outer Sleeve,and the interspace is then prepared on that side by utilizing a boringmeans such as, but not limited to, a Drill, Endmill, Reamer, or Trephineto drill, ream, or cut out the bone to be removed to either side, aswell as any remaining interposed discal material. In the preferredmethod, utilizing a specially designed Endmill-Drill, it and the InnerSleeve are removed as a unit, safely carrying away the bone and discdebris trapped within them from the spinal canal.

[0197] Step 7. If required, a thread forming Tap with penetrationlimiting means to control the depth of insertion, is then insertedthrough the Outer Sleeve.

[0198] Step 8. The prepared implant is then inserted utilizing thespecialized Driver unit. It should be noted that the implant may becoated with, and/or made of, and/or loaded with substances consistentwith bony fusion which may promote bone growth and/or fusion. However,in the preferred embodiment, the implant is treated with bone promotingand inducing substances, but is loaded with materials suitable forparticipating in a fusion.

[0199] While substances both natural and artificial are covered by thepresent invention, the preferred embodiment is in regard to the use ofthe patient's own bone by the following method. A hollow Trephine isutilized to harvest a core of bone from the posterior superior aspect ofthe iliac crest adjacent the sacroiliac joint. This core of bone is atits outside diameter, slightly smaller than the inside diameter of thespinal implant to be loaded, but longer than the spinal implant.Utilizing an instrument designed for that purpose, the core of bone isthen injected from within the Trephine into the central cavity of theimplant causing a superabundance of the bone material within the implantsuch that the bone material tends to press out through the openingscommunicating with the outside surface of the implant.

[0200] Step 9. Using the Driver Extractor instrument, the preparedimplant is threaded into the prepared interspace. The instrumentation isremoved from that side of the spine and attention is then redirected tothe first side of the spine. A small retractor is utilized to move thedural sac and traversing nerve root medially and to protect them andallowing the direct visualization of the retained Short Distractor unit.Without removing the Short Distractor, it is reassembled to its shaftportion, essentially reconstituting itself into a Long Distractor. Withthe inserted implant now acting as the distractor on the opposite side,the Long Distractor is utilized to guide the Outer Sleeve down where itis impacted as described in Step 5.

[0201] Steps 6 & 7 are then repeated, completing the procedure at thatlevel. The wound is then irrigated and closed in the routine manner.

[0202] Representative Example of The Preferred Method

[0203] Through preoperative templating of the patient's anteriorposterior, lateral, and axially imaged MRI scan in conjunction withtranslucent overlays of the various sized implants, the correct implantdiameter and length are accurately assessed, as well as the correctamount of distraction needed to restore the interspace to its premorbidheight. The patient is then properly positioned and a bilateral partialdiscectomy performed via paired semihemilaminotomies.

[0204] For the purpose of this example, it will be assumed that bypreoperative assessment it was determined that the correct implant wouldhave an external diameter of 18 mm and be 26 mm long. Further, thedistraction necessary to restore the height of the interspace would beapproximately 10 mm. The dural sac and traversing nerve root would thenbe retracted medially and protected, while a Long Distractor having anoutside diameter at the barrel portion corresponding to the implant tobe inserted, that is 18 mm, and having a diameter at the working end ofperhaps 8 mm, would be inserted. This then being found to be slightlysmaller than optimal by direct observation, a Convertible Distractorhaving in its barrel portion an 18 mm outside diameter, but having inits working portion a 10 mm diameter would then be inserted. Directobservation and/or x-ray then confirming the ideal distraction, theConvertible Distractor sould then be disassembled,-the barrel and headportion removed, and the Short Distractor portion left deeply embeddedand with its flanged head flat against the canal floor and deep to theneural structures. It would then be safe to allow the dural sac andnerve root to return to their normal positions, which would besuperficial to the flanged portion of the Short Distractor.

[0205] Attention would then be directed to the contralateral side. Thedural sac and nerve root would then be retracted medially on this secondside, and a Long Distractor with an 18 mm diameter barrel portion and a10 mm working portion would then be inserted into the interspace anddriven flush to the bone if necessary, such impaction imploding anyosteophytes not already removed, and assuring that the shoulder portionof the barrel comes to lie flat against the posterior aspects of theadjacent bodies. With the dural sac and nerve root still safelyretracted, the Outer Sleeve would then be placed over the LongDistractor and utilizing the Driver Cap and a mallet, seated to theoptimal depth.

[0206] In the preferred embodiment, the Long Distractor is then removedand the Inner Sleeve is inserted into the Outer Sleeve.

[0207] Since the purpose of the Inner Sleeve is to support the drill andallow for the increased size of the implant over the size of the drill,thus making it possible for the insertion of the implant to occurthrough the Outer Sleeve, the Inner Sleeve therefore measures 18 mm inits outside diameter, and 16.6 mm in its inside diameter. This allows itto fit within the Outer Sleeve, the diameter of which is 18.1 mm and toadmit the drill bit which is 16.5 mm in diameter.

[0208] Following the drilling procedure, the Drill and Inner Sleeve areremoved as a single unit with the trapped interposed cartilaginous andbony debris. The depth of drill penetration is preset and limited by thefixed rigid column of the Outer Sleeve. In this example, the space willhe prepared to a depth of 28 mm in anticipation of countersinking a 26mm long implant at least 2 mm. If a Tap were to be utilized, it would beinserted at this time and be appropriate to the minor and majordiameters of the implant to be inserted and as with the Drill,controlled for its depth of penetration. The spoinal implant would thenbe prepared for implantation by utilizing a Trephine to harvest a coreof posterior iliac bone greater than 30 mm, long and approximately 14.5mm in diameter.

[0209] Using the Bone Loading Device, this core of bone would beforcefully injected into the internal chamber of the spinal implantwhich would then be capped. Cap end forward, the fully loaded implantwould then be attached to the Insertion Driver, down the Outer Sleeveand screwed into place with the depth of penetration limited by theInsertion Driver. The Insertion Driver is then unscrewed from theimplant and removed from the Outer Sleeve. With the dural sac and nerveroot retracted and protected, the Outer Sleeve would then be removed.This would complete the fusion procedure on that side, and then asdescribed, the procedure would be repeated on the other (first) side ofthe same interspace.

[0210] Alternative Methods

[0211] An alternative and extremely useful method is the “TrephineMethod”. Its advantages include that it may be used in conjunction withthe preferred embodiment substituting the use of a hollow, tubularcutter, called a Trephine for the use of the Drill in Step 5 of thepreferred embodiment. Additionally, it may be utilized so as to obviatethe need for the placement of the Short Distractor and to allow theprocedure to be effectively performed from start to finish on one sideprior to initiating the procedure on the opposite side, and whilenevertheless maintaining distraction at the site of the bone removal.

[0212] The following is a description of the “Trephine Method”. Havingcompleted the exposure of the interspace on at least one side, the duralsac and nerve root are retracted. A Long Distractor differing from theLong Solid Bodied Distractor of the preferred embodiment only in thatthe barrel portion is of a precisely lesser diameter than the spinalimplant. As in the preferred embodiment, the Outer Sleeve has an innerdiameter only slightly greater than the implant to be inserted.Therefore, at this time, a first Inner Sleeve is inserted into the OuterSleeve to make up the difference between the outside diameter of theLong Distractor and the inside diameter of the Outer Sleeve. With theOuter Sleeve and first Inner Sleeve thus assembled, they are placed overthe Long Distractor and the Outer Sleeve is optimally seated using theImpaction Cap. The Cap and first Inner Sleeve are removed, but the LongDistractor and Outer Sleeve are left in place.

[0213] With the Long Distractor maintaining optimal distraction and withthe Outer Sleeve locking the vertebrae together so as to resist anymovement of the vertebrae, a hollow, tubular cutter known as a Trephineis then inserted over the Long Distractor and its barrel portion andwithin the Outer Sleeve. The Trephine, which is stopped out to theappropriate depth, can then be utilized to cut equal arcs of bone fromthe opposed vertebral endplates.

[0214] Alternatively, a second Inner Sleeve may be placed within theOuter Sleeve prior to placing the Trephine over the Long Distractor andwithin that second sleeve. This second Inner Sleeve would be justgreater in its internal diameter than the Long Distractor and justsmaller in its outside diameter than the inner diameter of the OuterSleeve. While it would provide enhanced stability to the Trephine,provision would then need to be made in the way of large flutes passinglongitudinally or obliquely along the outer surface of the Distractor toits barrel portion to accommodate the bony and cartilaginous debrisgenerated during the cutting procedure.

[0215] Following the use of the Trephine to the appropriate depth byeither of these methods, the Trephine, the Long Distractor, and thesecond Inner Sleeve, if utilized, are all removed. Since the Trephinecuts two arcs of bone but does not ream them out, a shafted instrumentwith a perpendicular cutting portion at its working end is then insertedparallel to the disc space and then rotated through an arc of motioncutting the bases of the two longitudinally cut arcs, thus freeing themfor removal through the Outer Sleeve. The space may then be tapped ifrequired, and the implant is inserted as per the preferred method. Asalready mentioned, the “Trephine Method” can be used with or without theuse of the Short Distractor on the contralateral side.

[0216] Applications of Method in Other Areas of the Spine

[0217] The following method is the preferred embodiment for performinganterior interbody fusion in the thoracic and lumbar spines. It is alsoappropriate in the cervical spine when the width of the spine anteriorlyis sufficient so that it is possible to place two implants side by sideand such that each intrudes at least several millimeters into thesubstance of the opposed vertebrae and for the length of the implants.

[0218] The interspace to be fused is adequately exposed and the softtissues and vital structures retracted and protected to either side.Visualization of the broad width of the interspace anteriorly is madepossible by the absence of the neurological structures in relation tothis aspect of the spine. The center line of the anterior aspect of theinterspace is noted and marked. The disc is removed using first a knifeand then curettes and rongeurs as needed. Alternatively, the disc may beleft intact to be removed during the drilling stage of the procedure.However, as per the preferred embodiment of the procedure, havingremoved the great mass of the nucleus and the greater portion of theannulus anteriorly, Long Distractors with progressively increasingdiameters to their working ends are inserted into the interspace at apoint midway between the central marking line and the lateral extent ofthe anterior aspect of the spine as visualized.

[0219] The Dual Outer Sleeve with its common Foot Plate and RetentionProngs is then inserted over either a singly placed Long Distractor andthen the second Distractor placed, or is placed over both Distractors ifalready placed. The Dual Outer Sleeve is then seated firmly against theanterior aspect of the spine. Any spurs which would interfere with theflush seating of the Foot Plate to the anterior aspect of the spineshould be removed prior to inserting the-Long Distractors. Once theOuter Sleeve has been optimally seated, one of the Long Distractors isremoved and in its place is inserted an Inner Sleeve and drill bit. Thedrill bit has as its outside diameter the minor diameter of the implantto be inserted. The Inner Sleeve is essentially equal in thickness tothe difference between the minor and major diameters of the threadedimplant.

[0220] A Stopped Drill is then utilized to prepare the opposed vertebralsurfaces and to remove any remaining disc material interposed. Ifrequired, a Stopped Tap may be inserted through the Outer Sleeve andinto the interspace to create a thread form. The properly preparedimplant is then affixed to the Insertion Driver and passed through theOuter Sleeve down into the interspace and inserted until its depth ofpenetration is limited by the stop on the Insertion Driver. With theimplant itself now in a position to act as a distractor, the LongDistractor is then removed from the contralateral side and the procedurerepeated. When both implants are firmly in place, the outer sleeve maythen be removed. The amount of countersinking of the implants may thenbe adjusted under direct vision.

[0221] Detailed Description of the Preferred Embodiment Method andInstrumentation

[0222] In the preferred embodiment, the disc (D) between adjacentvertebrae (V) is approached via bilateral paired semihemilaminotomies ofthe adjacent vertebrae. In the preferred embodiment the supraspinousligament, the interspinous ligament, the spinous process, portions ofthe lamina, and most of the facet joints are preserved. However, whileless desirable, these structures may be removed.

[0223] In the preferred method, a bilateral partial nuclear discectomyis then performed through bilateral openings created through theposterior aspect of the annulus fibrosus. While considered lessdesirable, disc excision can be delayed and performed simultaneouslywith the vertebral bone resection during the drilling procedure.Starting on the first side, a dural nerve root retractor is placed suchthat the dural sac and lower nerve root are retracted medially allowingexposure to one side of a portion of two adjacent vertebral bodies andthe interposed disc posteriorly.

[0224] Referring now to FIG. 1, preferably after removing some portionof nuclear disc material, a Long Distractor 100 is inserted under directvision into the intervertebral space. The disc penetrating portion 102is essentially cylindrical with a bullet-shaped front end 103 and ashoulder portion 104 where the penetrating portion 102 extends frombarrel 106. The penetrating portion 102 urges the vertebral bodiesapart, facilitating the introduction of the instruments. LongDistractors with sequentially increasing diameter penetrating portions102 are then introduced. As the optimal diameter of penetrating portion102 is achieved, the Vertebrae V to either side are forced into fullcongruence and thus become parallel, not only to the penetrating portion102, but to each other. At this time, any remaining excrescences of boneof the posterior vertebral bodies adjacent the posterior disc which havenot already been removed are flattened flush to the vertebral body bythe forced impaction, such as by hitting with a hammer flat surface 109of crown 110, driving the shoulder 104 against the lipped portions ofvertebrae V. Because of the forced opposition of the vertebral endplatesto portion 102 with optimal distraction, Long Distractor 100 will thencome to lie absolutely perpendicular to the plane of the posteriorbodies and absolutely parallel to the vertebral endplates, allowingoptimal alignment for the procedure to be performed.

[0225] Penetrating portion 102 is available in various diameters, butall are of a constant length, which is less than the known depth of theinterspace. This combined with the circumferential shoulder 104, whichis too large to fit within the interspace, protects against the dangerof overpenetration. Barrel 106 is of the same diameter as the externaldiameter of the device to be implanted. A recessed portion 108 below thecrown 110 allows for the Long Distractor 100 to be engaged by anextractor unit shown in FIG. 9.

[0226] Referring to FIG. 2, in the preferred embodiment, a ConvertibleLong Distractor 113 is used on the first side of the spine. TheConvertible Long Distractor 113 has a barrel portion 152 separable fromthe Short Distractor portion 120. While the initial distraction may beperformed with a solid Long Distractor, as the optimal distraction isapproached the appropriate Convertible Long Distractor is utilized. TheConvertible Long Distractor 113 consists of a Short Distractor portion120 and a barrel 152 having a rectangular projection 134 at one end. TheShort Distractor 120 has an increased diameter head 128, a rectangularslot 118 and an internal threaded opening 114. The barrel 152 is hollowand has an internal shaft 111 terminating in a large diameter hexagonalcrown 115 at one end and a reduced diameter portion 112. The crown 115has a detent portion 117 in its flat surface. The other end of the shaft111 has a threaded working end screw 116 that corresponds to threadedopening 114. The shaft 111 is prevented from removal from the barrel 152by set pin 119 passing through the wall of barrel 152 in a convenientmanner. The Short Distractor portion 120 is removably attached to thebarrel portion 152 via the mating of female rectangular slot 118 and themale mating member 134. The mating held together by utilizing knob 135to drive the crown 110 connected to interior shaft Ill having a threadedworking end screw 116 that threads into the female rectangular slot 118of the Short Distractor portion 120.

[0227] Knob 135 has an open socket 138 for fitting around crown 115 andengages the reduced diameter hexagonal portion 112 so as to permit therotation of shaft 111 and threaded working end screw 116. A detent ball150 in the inside of the socket 138 engages detent 117 in the crown 115,holding them together.

[0228] Referring, to FIGS. 2, 3, and 3A-3F the Short Distractor portion120 are designed to provide for high stability when temporarily situatedso as to resist inadvertent migration while the surgeon is working onthe second side. To that end, the embodiment of the Short Distractor 120shown in FIGS. 3 and 3A, has a pair of sharp pegs 126, to embed into theopposing vertebral bodies and forward facing ratchetings 124, thatfurther resist backward movement. FIGS. 3B and 3C, which show thepreferred embodiment, are side and top views of an alternativeembodiment of the distractor portion such that the distractor portion tobe interposed between the vertebrae is essentially cylindrical, but withcircumferential forward facing ratchetings 124.

[0229] Referring to FIGS. 3D and 3E, a further alternative embodiment ofthe Short Distractor is shown. This is a more rectangularized design,with forward facing ratchetings, without the sharp prongs 126 of FIG. 3.FIG. 3F is a side view of a further embodiment of the Short Distractor120 shown with knurling, to increase the interference with the bonesurface so as to add stability to the unit and to resist dislodgment. Tothis end, it is apparent that the working ends of both the Long andShort Distractors can have a variety of configurations consistent withtheir purpose, and that surface irregularities as well as the shape ofthe ends themselves, with or without prongs 126, may be utilized to makethe Short Distractor 120 more resistant to migration.

[0230] Once the ideal distraction has been achieved on the first side ofthe spine, the Convertible Distractor is dissociated, leaving ShortDistractor 120 in place with its rounded external end 128, safely on thecanal floor and deep to the dural sac and nerve root.

[0231] Referring to FIG. 4, the surgeon then moves to the other side ofthe spine at the same disc (D) level, and retracts the dural sac andnerve root medially, exposing the disc on that side. Long Distractors100 are then sequentially inserted into the disc space until thediameter of the distractor on the second side is at least as big as thaton the first side. If because of some asymmetry of the interspace, alarger diameter distractor is required on the second side to achieve theideal distraction as compared to the first side, then the second side isfitted with a Short Distractor of the larger diameter, and the surgeonwould then return back to the first side. In that event, the first sideShort Distractor would then be removed and the Long Distractor 100corresponding to the increased diameter of the already placed ShortDistractor 120 would then be inserted. In either event, the operation iscontinued by working on the one side where the Long Distractor is inplace. In this regard, it should be noted, that by the use of such adevice as the Michelson Otrhopedic Support Frame, U.S. Pat. No.4,481,943 issued on Nov. 13, 1984, it may be possible to obtain adequatedistraction preoperatively such that the surgeon is either disinclinedto use a distractor, or to simply place the correct Long Distractor onthe first side and then proceed with the surgical procedure on that sidebefore moving to the opposite side. These variations are within thescope of the present invention.

[0232] Referring to FIG. 5, the Long Distractor 100 now serves as both acentering post and an alignment rod for the hollow Outer Sleeve 140which is fitted over the Long Distractor 100, shown by phantom lines101. The front end of the Outer Sleeve 140 is metal and has sharp teeth142 that are capable of penetrating into and holding fast the twoadjacent vertebrae (V). Interrupting the circumferential sharp teeth 142are flat, planar areas 152 which serve to resist the further insertionof the sharp teeth 142 into the vertebral bodies. The sharp teeth 142 ofthe Outer Sleeve 140 are a continuation of the tubular shaft 144, whichin turn is connected to circumferentially enlarged tubular back end 146having a knurled outer surface 148 for easier manipulation. Analternative embodiment of an Outer Sleeve incorporates an expansible keyhole and slot configuration 154 to either side of shaft 144 along themid-plane of the interspace and parallel to it such that the end 142resists the collapse of the vertebrae (V) to either side of the disc(D), but may nevertheless allow for their further distraction, in theevent the only diameter or the root diameter of the implant is largerthan the hole drilled.

[0233] A Driver Cap 160 in the form of an impaction cap has at its farend a-flat, closed-back surface 162 and at its other end a broad,circular opening. The Driver Cap 160 fits over both the Outer Sleeve 140and the Long Distractor 100. As the Driver Cap 160 is seated, interiorsurface 170 circumferentially engages portion 146 of the Outer Sleeveuntil the back end 172 engages the internal shoulder 164. As malletblows are applied to surface 162, that force is transmitted via theinternal shoulder 164 to the Outer Sleeve 140 via its far end 172,seating sharp teeth 142 into the vertebral bodies adjacent the discspace D and to the depth of the teeth sharp 142 to the flat portions152. As the Outer Sleeve 140 is advanced forward, crown portion 110 ofthe Long Distractor is allowed to protrude within the Driver Cap 160unobstructed until it contacts the interior flat surface 168.

[0234] Referring to FIG. 6, once crown 110 comes into contact with theflat interior surface 168, then further taps of the mallet will notadvance the Outer Sleeve, any further motion being resisted by the flatshoulder portion 104 of the Long Distractor abutting the hard surfacesof the posterior vertebral bodies. In this way, the Outer Sleeve 140 issafely and assuredly inserted to its optimal depth and rigidly securingthe two opposed vertebrae as shown in FIG. 6.

[0235] Referring to FIG. 9, the Cap 160 is then removed and theDistractor Puller 200 of FIG. 9 utilized to remove the Long Distractor100 from the spine leaving the Outer Sleeve 140 in place. The DistractorPuller 200 has front portion 202, a mid portion 204, and a back handleportion 206. At the front portion 202 of the Distractor Puller 200, asocket 208 is connected to one end of shaft 210 which at its far end isconnected to back handle portion 206. The socket 208 has defined withinit a cavity 212 that is open at its front end and funnelized on theinterior aspect of its sides. The cavity 212 is constructed so that thehead of the Distractor Puller 200 and the partially circumferentialflange 218 engages the circumferential recess 108 of the Distractor 100.The entrance to cavity 212 is slightly funnelized, and the leading edgesof flange 218 slightly rounded to facilitate the engagement of recess108 and head 110 of Distractor 100, which is further facilitated in thatthe Driver Cap 160 leaves portion 108 of Distractor 100 precisely flushwith the back surface 172 of the Outer Sleeve 140. This provides alarge, flat surface 172 to precisely guide surface 230 of socket 208,and open portion 212 around head 110 while flange 218 engages recess108. The springloaded detent ball 228 engages hemispherical depression112 in the crown 110, shown in FIG. 2. This springloaded detent 228 inengagement with complimentary indent 218 protects against theinadvertent dissociation of the Long Distractor from the Puller 200after the Distractor has been removed from within the Outer Sleeve 140and prior to its removal from the wound. Once out of the body, the twoinstruments are easily disassociated by freeing the crown portion 110from cavity 212 by a manual force applied perpendicular to theirrelative long axes at this location.

[0236] A cylindrical and free removable weight 216 is fitted aroundshaft 210 between the front portion 202 and the rear handle portion 206.Gently, but repeatedly sliding the weight 216 along shaft 210 and drivenrearwardly against flat surface 228, transmits a rearward vector toproximal end 202 and thereby to the Long Distractor 100 to which it isengaged.

[0237] Paired extended handle 224 and 226, allow the surgeon to resistany excessive rearward motion as the instrument is used to liberate theLong Distractor 100. Paired handles 224 and 226 are also useful in thatthey allow a rotational directing of portion 208, via the shaft 210.This allows the surgeon to control and manipulate rotationally theorientation of the opening of cavity 212 to facilitate its application,to the head 110 of the distractor 100.

[0238] The Distractor Puller 200 is a significant improvement over thealternatives of striking a remover instrument with an independent hammerover the exposed surgical wound, or manually extracting the distractorby forcefully pulling. The use of a free hammer over the open wound isdangerous because the neural structures can be impacted on the backswing which is made even more likely by the effects of gravity on themallet head. Manual extraction by pulling is dangerous because of thesignificant interference fit of portion 102 within the spine such thatsignificant force would be required to remove the Distractor 100, and ifforce were not coaxial then the Outer Sleeve might be dislodged ormisaligned. Further, once the flat portion 102 became free of theinterspace, all resistance to withdrawal would be lost and in the faceof the considerable force necessary to free it, the Distractor 100 mighteasily become projectile imparting injury to the patient and/or thesurgeon.

[0239] Once the Long Distractor 100 has been fully removed from theOuter Sleeve 140, the toothed end 142 of the Outer Sleeve 140, workingin conjunction with the Short Distractor 120 on the contralateral siderigidly maintains the relative position of the adjacent vertebrae V.Further, since the remainder of the procedure on that side of the spineoccurs entirely through the protective Outer Sleeve 140, and as thenerves and dural sac are external to that Outer Sleeve and superficialto the toothed end 142 of the Outer Sleeve 140, which is firmly embeddedinto the adjacent vertebrae V, the Outer Sleeve 140 serves to insure thesafety of these delicate neural structures. Further, since the OuterSleeve 140 is of a fixed length and rigid, its flat rearward surface 172may be used as a stop to the advancement of all instruments placedthrough the Outer Sleeve 140, thus protecting against accidentaloverpenetration. Further, the Outer Sleeve 140 assures that the furtherprocedure to be performed will occur coaxial to the disc space D andfurther, be symmetrical in regard to each of the opposed vertebralsurfaces.

[0240] Referring to FIG. 10B, a posterior view of the spine at thisstage of the procedure, is shown with a Short Distractor 120 in place onone side of the spine and the bottom portion of Outer Sleeve 140 inplace on the opposite side of the spine.

[0241] Referring to FIG. 11A, an Inner Sleeve 242 is inserted from therear within the Outer Sleeve 140. This Inner Sleeve has a collar portion244 of a known thickness which seats against the top edge surface 172 ofOuter Sleeve 140. The cylindrical barrel portion of Inner Sleeve 242comes to approximate the posterior aspect of the vertebral bodiesinterior the Outer Sleeve when fully seated. A Drill 240, having a knownselected length is then introduced through the rearward aperture of theInner Sleeve 242 and utilized to ream out the arcs of bone which itengages from the opposed vertebral endplates as well as any discalmaterial within its path down to its predetermined and limited depth.The Drill 240, has a narrow engagement portion 246, which allows it tobe affixed to a drill mechanism which may be either a manual or a powerunit. A circumferential collar 248 of an increased diameter serves tolimit the depth of penetration of the drill 240 and may be fixed, orlockably adjustable.

[0242] Not shown here, but well known to those skilled in the art, arevarious mechanisms to lockably adjust such instruments as is drills.Such mechanisms include, but are not limited to, the use of collets,threaded shafts with lock nuts, and flanges engaging grooves forcedtherein by either a cap pulled over the flanges or screwed down uponthem.

[0243] In the preferred embodiment, the forward cutting edge 252 ofDrill 240 is a modification of a large fluted drill design such that theend resembles an end cutting mill which may contain any workable numberof cutting surfaces, but preferably four or more, and such cuttingsurfaces being relatively shallow such that the advancement of theinstrument occurs more slowly. The outside diameter of the Drill 240corresponds to the minor diameter of the threaded spinal implant. TheInner Sleeve 242 has an inner diameter slightly greater than thatdimension and its outer diameter is slightly smaller than the insidediameter of the Outer Sleeve 140 which has the same outer diameter asthe major diameter of the threaded implant.

[0244] The drill shaft of drill 240 comprises an upper portion 243, acentral recessed portion 256 of a smaller diameter and a lower cuttingdrill portion 250. The upper portion 243 and lower portion 256 of thedrill 240 have the same outside diameter.

[0245] The Inner Sleeve 242 serves many functions. First, it provides amore intimate drill guide for drill 240 in the event a smaller diameterhole is to be drilled than that of the inside diameter of the OuterSleeve 140. Second, since it now guides the Drill, it allows for theOuter Sleeve 140 to have an internal diameter large enough to admit thethreaded spinal implant, which is indeed considerably larger in diameterthan the Drill 240 itself.

[0246] If a larger Outer Sleeve 140 were utilized absent the InnerSleeve 242, then the Drill 240 would be free to wander within theconfines of that greater space and would not reliably make parallel cutsremoving equal portions of bone from the adjacent vertebrae V. Further,the bone removal not only needs to be equal, but must be correctlyoriented in three dimensions. That is, the path of the Drill 240 must beequally centered within the disc space, parallel the endplates, andparallel to the sagittal axis dissecting the interspace.

[0247] A further purpose of the Inner Sleeve 242 is that it may beremoved simultaneously with the Drill 240, thereby trapping the debris,both cartilaginous and bony generated during the drilling procedure,which are guided rearward by the large flutes 251 of Drill portion 250,where they are collected around recessed portion 256 between therecessed portion 256 and the inner wall of the Inner Sleeve 242 arethere contained therein. Thus, by removing the Drill 240 in conjunctionwith the Inner Sleeve 242, all of the debris generated by the reamingprocedure is safely removed from the spinal canal and wound area.

[0248] Further, if the disc tissue in the area to be reamed has beenremoved previously, as per the preferred method, then the patient's ownbone of good quality and useful within the operation will then becontained between the Inner Sleeve 242 and the shaft portion 256. Onceaway from the surgical wound, this material may be used to load thespinal implant or placed deep within the interspace to participate inthe fusion.

[0249] The method of actually producing the surgical hole within thespine is variable. As shown in FIG. 11C, in an alternative embodimentDrill end 250 has a forward projecting nipple 260, which itself isbullet-shaped in its leading aspect so as to ease its entrance into thedisc space and to urge the vertebrae apart. Nipple 260 is distracting,stabilizing as it resists any tendency of the vertebrae to movetogether, is self-centering to the Drill portion 250 when working inconjunction with Sleeves 140 and 242, and virtually assures thesymmetrical resection of bone from the opposed vertebral surfaces.

[0250] Referring to FIG. 11B, the alternative “Trephine Method” referredto earlier in this application is shown. In this alternative, a LongDistractor 100 is left in place after the Outer Sleeve 140 is seated.The Long Distractor 100 in this case differs from the Long Distractor ofthe preferred embodiment in that its outside diameter of the barrel 106is of a smaller diameter than in the prior version. This is madenecessary because regardless of the method, the hole to be formedcorresponds to the minor diameter of the spinal implant. Trephine 270, ahollow, tubular member with sharp cutting teeth 251 at its proximal end,has a wall thickness and since the outside diameter of that trephine 270must correspond to the root diameter of the implant, then the wallthickness of the trephine 270 must be allowed for by a correspondingreduction in the diameter of the Long Distractor 100.

[0251] A further modification of the Long Distractor 100 to the“Trephine Method” would use longitudinal grooves (not shown) along thebarrel surface 106 for the purpose of transmitting any debris generatedduring the cutting procedure, rearward. Since the cutting element isboth centered and aligned by the Long Distractor, the use of the InnerSleeve 242 is not mandatory, but may once again be useful in controllingthe path of the debris. To that end, little debris is generated in the“Trephine Method” as the bony arcs are not so much being reamed out andremoved as they are simply being cut into the bone where these arcs ofbone are left connected at their far ends. Thus, when the TrephiningMethod has been completed and the Trephine 270 and Inner Sleeve 242removed, unlike in the preferred embodiment where the hole is drilledout, it remains necessary to remove both the two arcs of bone, and anyinterposed material. Nevertheless, this is very easily performed byvarious means, one of which is depicted in FIG. 11D.

[0252] Referring to FIG. 11D, Instrument 272 consisting of a shaft 276attached off-center to the lower surface 273 handle 274 is shown. Theshaft 274 terminates in a cutting arm 278. The instrument 272 isinserted through Outer Sleeve 140 where the lower surface 273 of handle274 abuts the top 172 of the Outer Sleeve 140, both stopping downwardmotion of instrument 272 and precisely placing the perpendicularlycutting arm 278 of instrument 272 so that as handle portion 274 isrotated, the cutting arm 278 is also rotated, cutting the arcs of boneand liberating them from their last attachments. These portions of boneare then removed utilizing this instrument or a long forceps, and thenplaced within the implants or otherwise used to participate in thefusion.

[0253] Referring to FIGS. 12 and 13, while in the preferred embodimentof the present invention the spinal implant I, is essentiallyself-tapping, if the bone is unusually hard it may be desirable to formthe thread pattern within the interspace prior to the insertion of theimplant I. To that end, as shown in FIG. 12, Tap 280 has a threadcuttingportion 282 connected by a shaft 286 to a handle portion 292, which hasbeen designed to give mechanical advantage to the rotation of theinstrument for the purpose of cutting threads. The lower portion ofhandle 290 has a forward facing flat surface 288 too large to fitthrough the opening of Outer Sleeve 140 which thus safely limits thedepth of penetration of the cutting element 282. This tap 280 is furthermade safe by blunt end 294 which will engage the uncut portions of thevertebral bone just prior to the engagement of shoulder 288 againstsurface 172. This feature allows the surgeon to appreciate a less harshresistance as the blunt nose 294 encounters the remaining unresectedbone for the drill hole and prior to the sudden increase in resistancecaused by the seating of shoulder 288 against top edge 172, which firstresistance serves as a warning to the surgeon to discontinue the tappingprocedure. Thus, the surgeon has both visual (as shoulder 288 approachestop edge 172) and tactile warnings to avoid stripping the thread form.Tap end 282 is highly specialized for its specific purpose. Rearward tothe specialized blunt tip 294 is a truncated bullet-shaped area 298which ramps up to the constant diameter intermediate the cutting ridges296. Ramp portion 298 urges the opposed vertebral bodies apart, whichmotion is resisted by Outer Sleeve 140, thus progressively driving thesharp leading edges of thread forms 296 into the vertebral bodies. Theperiodic longitudinal grooves 284 interrupting the thread forms, whichmay number 1 to 8, but preferably 4, function to accumulate the bonymaterial which is removed during the thread cutting process. In thatregard, in the ideal embodiment, the thread cutting form is designed tocompress the bone to be formed rather than to trough through it.Further, while both the major and minor diameters of the Tap 280 may bevaried, in the preferred embodiment, the minor diameter corresponds tothe minor diameter of the implant I, but the major diameter is slightlyless than the major diameter of the implant.

[0254] With Tap 280 now removed, and Sleeve 140 still in place, thesurgical site is now fully prepared to receive the spinal implant I. Inthe preferred embodiment of the spinal implant, the implant has beenenhanced by the use of, application to, and filling with fusionpromoting, enhancing, and participating substances and factors. Thus,the implant may be fully prepared for insertion as provided to theoperating surgeon. However, at the present time, human bone is mostcommonly used as the graft material of choice, with the patient's ownbone being considered the best source.

[0255] Referring to FIG. 14A, a trephine 300 is shown with anexceedingly sharp front cutting edge 302 for quickly and cleanly coringinto the patient's posterior iliac crest, or any other bony tissue, andfor the purpose of producing a core of bone then contained within thehollow 304 of the trephine 300. Trephine 300 has a rear portion 306 witha pair of diametrically opposed slots 310, and disposed clockwise fromtheir longitudinally oriented rearward facing openings so as to engagediametrically and opposing members 312 of Drive. Unit 308, by whichtrephine 300 may be attached to either a hand or power drill. It can beappreciated that engagement mechanism 312 is stable during the clockwisecutting procedure, and yet allows for the rapid disconnection of the twocomponents once the cutting is completed.

[0256] Because of the high interference between the graft and the innerwall of hollow portion 304, and the relative weakness of the cancellousbone being harvested, it is possible to remove the Trephine 300 whilestill drilling, and to have it extract the core of bone with it.However, in the highly unlikely event that the core of bone would remainfixed at its base, then with the drive mechanism 308 removed, acorkscrew 408 shown in FIG. 14C is introduced though the central openingof rear portion 306 and threaded down and through the core of bonewithin 304 and to the depth of teeth 302. The tip 318 of the corkscrew408, which extends substantially on line with the outer envelope of thecorkscrew, then cuts radially through the base of the bone core. As thehandle portion 314 of the corkscrew 408 abuts the flat, rearward surfaceof portion 306 and it can no longer advance. As corkscrew 408 iscontinued to be turned further, it will cause the core of bone to bepulled rearward, as in removing a cork from a wine bottle. Trephine 300has a barrel portion 304 continuous with sharp toothed portion 302having an inner diameter just less than the inner diameter of the spinalimplant I to be loaded.

[0257] Referring to FIG. 14B, the Trephine 300 with its core ofharvested bone is then placed as shown in FIG. 14B, through opening 340of Implant Bone Loading device 320, where the barrel portion 304 thenpasses through and is stopped by circular flange 344. The plunger shaft326 of instrument 320 is then prepared for attachment by rotating knob332 counterclockwise such that the plunger 372 is pulled via the longthreaded shaft portion 328 back to the base of collar 330 at itsproximal end. In this position, knob 332 is considerably extendedrearward from collar 330. With plunger shaft 326 in this position, theplunger head 372 is inserted into the central hollow of portion 306 ofTrephine 300 as the proximal cylindrical portion of collar 330 thenfollows it, such that the plunger 372 then occupies the rearward portionof barrel 304 and the proximal cylindrical portion of collar 330occupies the central hollow of portion 306. A pair of diametricallyopposed radially projecting arms 346 on collar 330 are then advancedlongitudinally into diametrically opposed paired L slots 340 and thenrotated clockwise to complete this assembly.

[0258] At the other end of instrument 320, a spinal implant I is engagedthrough its female rectangular slot 364 by a rectangular protruding barextending from rearward facing surface of end plug 324, (not shown) andsecured there by knob 334 which extends as a rod through a centralaperture within end plug 324 to extend at the far end as a small boltwhich threads to a female aperture centered within the female slot 364of the spinal implant. With the spinal implant I secured to end plug 324and the opposite end of the implant I presenting as a hollow, tubularopening, end plug 324 is advanced into device 320 where it is secured byrotationally engaging diametrically opposed L-shaped slots 321. Withdevice 320 fully assembled, end 302 of trephine 300 lies coaxial andopposed to the open end of implant I.

[0259] Referring to FIG. 15, as knob 332 is then rotated clockwise, theplunger 372 proximal the threaded shaft 328 is then forcibly, butcontrollably driven forward down the barrel 304 ejecting the bone graftdirectly into the spinal implant I. As the bone graft is greater inlength than the interior of the spinal implant, with further compressionthe bone is forced into the radially disposed apertures through the wallof the device communicating from the central cavity to the exterior.

[0260] End plug 324 is then removed from apparatus 320. Using end plug324 as a handle, end cap 374 shown in FIG. 16 is secured to the open endof the spinal implant I. The implant is then disassociated from end plug324 by rotating knob 334 counterclockwise.

[0261] Referring to FIG. 16, an Implant Driver instrument which may beused to either insert or to remove said implant I is shown. Driver 350has at its far end 362, a rectangular protrusion 398, which protrusionintimately engages the complimentary rectangular slot 364 of implant I.Protruding from slot 398 of end 362 is threaded portion 353, whichextends as a rod through hollow shaft 358 and hollow hand barrel 360 toknob 354 where it can be rotationally controlled. Threaded portion 353screws into a female aperture central slot 364, urging 353 into 364, andbinding them together such that instrument 350 can be rotated via pairedand diametrically opposed extending arms 366 and in either directionwhile maintaining contact with the implant.

[0262] Referring to FIG. 17, affixed to the Driver 350, the implant I isthen introduced through the Outer Sleeve 140 and screwed into theinterspace opposed between the two prepared vertebrae V until such timeas the leading edge of the Implant Cap 374 reaches the depth of theprepared hole at which time its forward motion is impeded by the bonelying before it which had not been drilled out. This allows for aprogressive feel to the surgeon as the implant is screwed home.

[0263] As described previously, with the use of the Tap 280, thisterminal resistance to further seating provides significant tactilefeedback to the surgeon. Again, as with the Tap 280, visual monitoringof the depth of insertion of the implant is provided to the surgeon byobserving the progressive approximation of the forward surface 370, ofbarrel portion 360, as it approaches the rearward facing surface 172 ofOuter Sleeve 140. Nevertheless, a final safety mechanism, when the fulldepth of insertion has been achieved, surface 370 of instrument 350 willabut surface 172 of the Outer Sleeve 140, prohibiting any furtherinstallation of the spinal implant.

[0264] Referring to FIG. 18, once the implant has been fully installed,the Driver 350 is dissociated from the implant I by turning knob 354 ina counterclockwise direction. The Driver 350 is then withdrawn from theOuter Sleeve 140, then the Outer Sleeve 140 is removed. This leaves theimplant fully installed and inset to the determined depth as shown inFIG. 18.

[0265] Attention is then redirected to the other, or first, side of thespine. A dural nerve root retractor is used to retract the neuralstructures medially, bringing into full view the head 128 of the ShortDistractor 120, lying flush on the canal floor. Utilizing apparatus 152,extended screw portion 116 is inserted into the female threaded portion114 of the Short Distractor 120 as the extended rectangular portion 134of apparatus 152 is engaged to the female rectangular portion 118 of theShort Distractor 120. Then turning rearward facing portions 108 and 110,utilizing the knob 136 of FIG. 2, the Long Distractor configuration isrestored.

[0266] With the dural sac and nerve roots still retracted and protected,the Outer Sleeve 140 is slipped over the reconstituted Long Distractorand seated using the Driver Cap 162. The entire sequence of events asdescribed for the implantation of the spinal implant I-as-alreadyplaced, is then repeated such that both spinal implants come to lie sideby side within the interspace. Though not necessary, circlage or otherinternal fixation of the levels to be fused may additionally beperformed, and then the wound is closed in the routine manner.

[0267] Brief Discussion With Reference To The Drawings of The PreferredMethod And Instrumentation For Anterior Interbody Fusion IncorporatingIntercorporeal Predistraction And Utilizing A Guarded Sleeve System IsDisclosed

[0268] Because of the absence of the spinal cord and nerve roots, it isgenerally possible to visualize in one instance the entire width of thedisc space from side to side throughout the cervical, thoracic, orlumbar spine. In the preferred embodiment of the anterior interbodyfusion, implants are placed side by side from anterior to posteriorparallel to the interspace and extending into the adjacent vertebralbodies. Where the transverse width of the disc space is insufficient toallow for the use of two implants, each of which would be large enoughto protrude to the required depth into the adjacent vertebrae, then asingular and significantly larger implant may be placed centrally. Withthis in mind, and in light of the very detailed description of thetechnique and instrumentation already provided in regard to the methodof posterior lumbar interbody fusion, a brief discussion of anteriorspinal interbody fusion with dual implant installation will suffice, andthe method for installation of a large, singular midline graft willbecome obvious.

[0269] The interspace to be fused is exposed anteriorly. The softtissues are withdrawn and protected to either side, and if necessary,above and below as well. It is then possible to visualize the entirewidth of the vertebrae anteriorly adjacent that interspace. As discussedabove, the surgeon has already templated the appropriate patientradiographs to determine the requisite distraction and optimal implantsize. In the preferred method, the surgeon then broadly excises thegreat bulk of the nuclear disc portion. (Alternatively, the disc can beleft to be removed via the drill later.) The surgeon then notes andmarks a point midway from side to side anteriorly. He then inserts LongDistractor 100 centering it on a point midway between the point justnoted and the lateral extent of the intervertebral space visualizedanteriorly. The outer barrel portion 106 of the Distractor 100 utilized,will correspond to the outside diameter of the implants to be installed.The Distractor tips 102 inserted are sequentially larger in diameteruntil the optimal distraction is achieved. This optimal distraction,although suggested by the initial templating, may be visually andtactilely confirmed as performed. When the optimal distraction isachieved, the vertebral endplates will come into full congruence andparallel to the forward shaft portion 102 of the Distractor 100, causingan alteration in the alignment of the vertebrae and a significantincrease in the interference fit and pressurization at the tip, suchthat the instrument becomes exceedingly stable.

[0270] There is a sensation imparted to the surgeon of the tissueshaving moved through their elastic range to the point where the twoadjacent vertebrae V begin to feel and move as if a single solid. Thesechanges are easily appreciated visually as the vertebrae realign tobecome congruent to tip 102, and can also easily be appreciated vialateral Roentgenography. However, should the surgeon fail to appreciatethat optimal distraction has been achieved and attempt to furtherdistract the interspace, he would find that extremely difficult to dobecause of the increased resistance as the tissues are moved beyondtheir range of elastic deformation. Further, there would be noelasticity left to allow the vertebrae to move further apart and thesensation to the surgeon should he attempt to gently tap the oversizedDistractor forward with a mallet, would be one of great brittleness.

[0271] Returning now to the procedure, when the correct intercorporealLong Distractor 100 producing the ideal interspace distraction-havingits barrel portion 106 corresponding to the implant I to be installedhas been inserted, then its exact duplicate is inserted anteriorlyequidistant to the other side of the spine. As the barrel portion 106 ofLong Distractor 100 is exactly of the same major diameter as the spinalimplant I looking coaxially on end, the surgeon can then asses theanticipated side by side relationship of the dual implants whenimplanted.

[0272] Referring to FIGS. 7C and 7D, a Dual Outer Sleeve 340 consistingof a pair of hollow tubes is then introduced over the side by side LongDistractors 100 protruding anteriorly from the spine. The Dual OuterSleeve 340 is comprised of two hollow tubular members identical in sizedisplaced from each other ideally the sum of the difference between theminor and major diameters of both implants combined, but not less thanthat difference for one implant, as it is possible to have the threadsof one implant nest interposed to the threads of the other, such thatthey both occupy a common area between them. However, while thepreferred embodiment is slightly greater than two times the differencebetween the major and minor diameters of the implant (the sum of both)the distance may be considerably greater. Whereas in the preferredembodiment the paired tubular portions 348 of the Dual Outer Sleeve 340are parallel, when the area between them 350, is sufficiently great,these elements may be inclined or declined relative to each other suchthat they either converge or diverge at their proximal ends. The pairedtubular portions 348, may be bridged in part or wholly throughout theirlength, but are rigidly fixed by Foot Plate 344. In its preferredembodiment, a top view shows the Foot Plate 344 to be essentiallyrectangular, but without sharp corners. However, it is appreciated thatother shapes for the Foot Plate 344 can be utilized.

[0273] Referring to FIG. 7D, it can be appreciated, that Foot Plate 344is contoured so as to approximate the shape of the vertebrae anteriorly.Extending forward from Foot Plate 344 are multiple sharp prongs 342sufficiently long to affix them to the vertebrae. The prongs 342 arelimited in length so as to not penetrate too far posteriorly and numberfrom 2 to 10, but preferably 6.

[0274] Referring to FIGS. 7E and 7F, as the Dual Outer Sleeve 340 isdriven forward utilizing Dual Driver Cap 420, of FIG. 7E, engaging therearward end 352, the prongs 342 extending from Foot Plate 344 areembedded into the opposed vertebral bodies until their forward motion isinhibited by the curved Foot Plate 344 becoming congruent to and beingstopped by, the anterior aspect of the vertebral bodies.

[0275] As already shown in FIG. 5, the Dual Driver Cap 420 is of thesame design as Single Driver Cap 160, in that there is a recess 354 asper 168, allowing the Outer Sleeve to be fully seated without impedingthe rearward projection of the Long Distractor unit. However, unlike inCap 160, area 354 is more relieved as it is unnecessary for the Dual Cap420 to contact the Long Distractor through portion 110 to inhibit itsforward motion, as the Foot Plate 344 functions to that effect. Further,the Dual Cap 420 for the Dual Outer Sleeve 340 is correspondingly dualitself and engages the rearward facing dual tubular portion 352. Oncethe Dual Outer Sleeve has been fully seated, the vertebrae adjacent theinterspace to be fused are rigidly held via Foot Plate 344 and theprongs 342. Thus, it is possible to remove either one, or if desired,both of the Long Distractor rods utilizing Long Distractor puller 200,as per the method already described. It is then the surgeon's choice towork on one or both sides of the spine. As per previous discussion, thesurgeon may drill the interspace utilizing the Inner Sleeve 242 or leavethe Long Distractors in place as per the “Trephine Method”.

[0276] Tapping, if necessary, and the insertion of the implants thenoccurs through the protective Outer Sleeve 340. Once the implants havebeen fully inserted, the Outer Sleeve is removed.

[0277] Having utilized the Drill method, or “Trephine Method”, with orwithout an Inner Sleeve to prepare the fusion site, it is the preferredembodiment to leave the Outer Sleeve 340 in place as it provides for theideal placement and alignment of the Tap 280 and implant I.

[0278] It is anticipated that the surgeon wishing to work deep withinthe interspace, or preferring the ability to directly visualize the tapbeing used, or the implant being inserted, may choose to remove theOuter Sleeve after the insertion of the first prosthesis to maintainstability, or prior to that, which while not the preferred embodiments,are nevertheless within the scope of the present invention.

[0279] Alternative Methods To The Preferred Embodiment For Method OfAnterior Interbody Fusion

[0280] As previously described for the posterior lumbar spine,alternatively, one can employ the “Trephine Method” as has beendescribed in detail.

[0281] As a further alternative, it should be noted that the key elementin the anterior method is the use of the predistraction principle, wheresuch distraction is maintained by the Outer Sleeve with or without theLong Distractor. Therefore, once the preparation of the interspace hasbeen completed, while not the preferred embodiment, it is neverthelesswithin the scope of this invention that one could remove the OuterSleeve as there are no neural structures requiring protection, andinsert the implants directly rather than through the Outer Sleeve.

[0282] As yet a further alternative of this method, where the height ofthe distracted interspace is such that the diameter of the implantrequired to span that height and to embed with sufficient depth into theopposed vertebral bodies is such that it is not possible to place twosuch implants side by side, then only a single implant which may be ofsignificantly increased diameter, is used and placed centrally withinthe interspace rather than to either side. The placement of a singularcentral graft via the present invention method and instrumentation is inkeeping with the methods already described and can be performed usingeither a drill or the “Trephine Method”.

[0283] Referring to FIGS. 16-18, a cylindrical embodiment of the spinalimplant I of the present invention is shown. In FIG. 16 the implant I isshown attached to the insertion device 350. In FIGS. 17 and 18 theimplant I is shown installed in the disc space D, between the adjacentvertebrae.

[0284] The cylindrical implant I comprises a hollow tubular member whichin the preferred embodiment is made of an ASTM surgically implantablematerial, preferably titanium. The cylindrical implant I is closed atone end and open at the other end covered by a cap 394. The cylindricalimplant I has a series of macro-sized openings 390 through the sidewalls of the cylindrical implant I. A series of external threads 392 areformed on the circumference of the cylindrical implant I. Any variety ofthreads may be used on the implant. The cap 374 has a hexagonal opening394 for tightening the cap 374.

[0285] While the present invention has been described with respect tothe preferred embodiment of the method and instrumentation, it isappreciated that other embodiments of the method and instrumentation maybe devised without departing from the scope of the present invention.Examples of further embodiments of the present invention are describedin detail below.

[0286] Detailed Description of Alternative Embodiments of Apparatus andMethod

[0287] When the human spine is viewed from the side, it consists of abalanced series of curves, as opposed to the vertebrae being stacked oneupon another in a straight line when viewed from the side. In both thecervical and lumbar regions of the spine, the vertebrae relate to eachother so as to form curves where the apex of said curves is displacedforward within the body, and those segments of the spine are said to bein lordosis. In contradistinction, in the thoracic portion of the spine,the vertebrae relate to each other so as to form a curve where the apexof said curve is displaced posteriorly and is said to be in kyphosis.The methods and instrumentation of the present invention have as one ofits purposes to provide for the permanent stabilization of contiguousvertebrae by fusion, there is then a need for a means to preserve saidlordosis/kyphosis if present, or to restore said lordosis/kyphosis ifalready lost, prior to the completion of the fusion procedure.

[0288] The following embodiments of the present invention, eitherindividually or in combination, provide for both the stabilization andfusion to be performed with the related vertebrae in the correctanatomic lordosis or kyphosis. Where it is possible to approach thespine from various angles each of the devices, then has different formsappropriate to that specific approach.

[0289] Referring to FIG. 19, an alternative embodiment of theinstrumentation of the present invention comprising a Posterior LongLordotic Distractor 400 capable of restoring and maintaining lordosis ofadjacent vertebrae V from the posterior approach of the spine is shown.The Posterior Long Lordotic Distractor 400 is inserted from theposterior aspect of the spine and comprises a barrel portion 410terminating at its distal end 412 in a disc penetrating portion 420which is shown interposed within the disc space between two adjacentvertebrae V. The disc penetrating portion 420 terminates distally into aleading bullet-shaped front end 422 which facilitates the insertion ofthe disc penetrating portion 420 between the adjacent vertebrae V. Thedisc penetrating portion 420 is configured to have an uneven diametersuch that it has a lesser diameter, and thus a lesser height within thedisc space proximate the distal end 412 of the barrel portion 410 andhas a greater diameter, and thus greater height within the disc space,in the direction of the front end 422. This configuration of the discpenetrating portion 420 serves to not only restore the intervertebraldisc space height upon insertion of the disc penetrating portion 420 ofthe Posterior Long Lordotic Distractor 400, but also serves to restoreand maintain the normal lordosis between the adjacent vertebrae V. Theleading bullet-shaped front end 422 is of particular importance inregard to the Posterior Long Lordotic Distractor 400 where the largestdiameter portion of the disc penetrating portion 420 would otherwise beentering the disc space first.

[0290] The widest diameter of the disc penetrating portion 420 is lessthan the diameter of the barrel portion 410, such that a circumferentialshoulder 424 is formed at the distal end 412 of the barrel portion 410which prevents over penetration into the disc space of the PosteriorLong Lordotic Distractor 400. It can readily be appreciated that such aconfiguration of the disc penetrating portion 420 renders the PosteriorLong Distractor 400 quite stable within the disc space and resistant tobacking out as the compressive forces of the spine upon the discpenetrating portion 420 tend to urge it forward, while simultaneouslythe circumferential shoulder 424 makes such further motion impossible,thus making the Posterior Long Distractor 400 exceedingly stable.

[0291] Referring to FIG. 20, in preparation for the bone removal step,the Posterior Long Lordotic Distractor 400 is shown with the discpenetrating portion 420 in place between the adjacent vertebrae V torestore and maintain lordosis of the spine. An Outer Sleeve 140described above in reference to FIG. 5, is properly seated over thePosterior Long Lordotic Distractor 400 using a mallet and the alreadydescribed Driver Cap 160. While the bone removal step may be performedby either the drilling method described above in reference to FIGS. 11Aand 11C or the “Trephine Method” described above in reference to FIG.11B, the “Trephine Method” is preferred in this situation as it leavesthe Posterior Long Lordotic Distractor 400 undisturbed until sufficientspace has been created by the removal of bone at least as great as thethickness of the wall of the trephine 270 itself to allow for theunobstructed removal of the Posterior Long Lordotic Distractor 400.

[0292] If the “Trephine Method” described above in reference to FIG. 11Bis used with the Posterior Long Lordotic Distractor 400 the Outer Sleeve140 would first be fitted with an Inner Sleeve 242 such as that shown inFIG. 11B, prior to both being placed simultaneously down over the barrelportion 410 of the Posterior Long Lordotic Distractor 400. Once theOuter Sleeve 140 is concentrically seated relative to the barrel portion410, the Inner Sleeve 242 alone would be removed, and the trephine 270would then be placed over the Posterior Long Lordotic Distractor 400 andwithin the confines of the Outer Sleeve 140 and into the adjacentvertebrae V across the disc space to the appropriate depth. The use ofan Inner Sleeve is not required as the trephine 270 is both centered andaligned by the Posterior Long Lordotic Distractor 400.

[0293] In addition to cutting the two hemi-cylinders of bone, one foreach vertebrae V, the saw-like sharp cutting teeth 271 of the trephine270 shown in FIG. 11B removes a path of bone equal to the distance ofthe splaying out of each of the cutting teeth 271 relative to itsneighbor and which distance cannot be less than the wall thickness ofthe trephine 270 itself. Thus, once the trephine 270 is removed, leftbehind is a semi-cylindrical space outlining each of the arcs of bonecut from the adjacent vertebrae V such that the two spaces combinedprovide for sufficient space such that it is then possible to extractthe Posterior Long Lordotic Distractor 400 without disturbing thevertebrae V themselves as the vertebrae V are held in position by theOuter Sleeve 140 which engages both of the vertebrae V.

[0294] Referring to FIGS. 21 and 22, since the vertebrae V are placedinto lordosis prior to the bone removal step, the space S created by thebone removal is cut at an angle relative to the vertebrae V in the shapeof a cylinder, and which corresponds to the shape of the cylindricalimplant I. In this manner, the cylindrical implant I with parallel wallsmay be inserted between adjacent vertebrae V which have been stabilizedfor fusion in angular relationship to each other so as to preserve thenormal curvature of the spine.

[0295] Referring to FIGS. 23 and 24, an elevational side view and a topplan view, respectively, of a Posterior Short Lordotic Distractor 500for posterior use generally referred to by the numeral 500 is shown. ThePosterior Short Lordotic Distractor 500 is similar to the ShortDistractor 120 described above in reference to the ConvertibleDistractor and comprises a disc penetrating portion 520 identical tothat of the Posterior Long Lordotic Distractor 400 and an increaseddiameter head 128 as described above in reference to FIGS. 3-3F. Asdiscussed above for the Posterior Long Distractor 400, the configurationof the disc penetrating portion 520 renders the Posterior Short LordoticDistractor 500 quite stable. This is an especially important feature forthe Posterior Short Lordotic Distractor 500 because it is left under thedelicate dural sac and nerves while work is being performed on thecontralateral side of the spine. If the Posterior Short LordoticDistractor 500 were other than stable, injury to these structures mightresult. To further prevent unwanted backing out of the Posterior ShortLordotic Distractor 500, the bone engaging surface 530 may be knurled orotherwise roughened, or have forward facing ratchetings.

[0296] Referring to FIG. 25, an Anterior Long Lordotic Distractor 600for use anteriorly within the spine is shown. It can be seen that theconfiguration of the disc penetrating portion 620 is the reverse of thedisc penetrating portion 420 of the Posterior Long Lordotic Distractor400 in that the disc penetrating portion 620 is of greatest diameter andheight proximate the barrel portion 610 and that the diameter and heightare diminished more distally in the direction towards the front end 622along the disc penetrating portion 620. The Anterior Long LordoticDistractor 600 serves to restore and maintain lordosis of the spine bydistraction of the adjacent vertebrae V. As described above for thePosterior Short Lordotic distractor 500, it is appreciated that anAnterior Short Lordotic Distractor (not shown) having a disc penetratingportion 520 may be similarly devised.

[0297] It can be seen that all of the Lordotic distractors, both theanterior and the posterior embodiments, have specialized leadingbullet-shaped or nosecone-shaped portions so as to facilitate theinsertion of the disc penetrating portions within the disc space. Thisis of particular importance in regard to the Posterior LordoticDistractors where the largest diameter portion of the disc penetratingportion 420 would otherwise be entering the disc space first.

[0298] Referring to FIGS. 26 and 27, an alternative embodiment of thepresent invention for maintaining distraction during the surgicalprocedure involves a more specialized form of the previously describedOuter Sleeve 140 and is shown and identified as the Extended OuterSleeve 700. The Extended Outer Sleeve 700 comprises a hollow tubularmember 702 having a distal end 710 which has been extended such that apair of extended portions 720 and 722, which are essentially acontinuation of the hollow tubular member 702 itself (with or withoutreinforcement), are opposed 180 degrees from each other, tapered attheir leading edges 724 and 726 for ease of introduction, and of suchheight as to restore the height of the intervertebral disc space.Located at the distal end 710 may be a plurality of teeth 712, similarto those previously described above, or other engagement means forengaging the bone of the adjacent vertebrae V. It appreciated that thedistal end 710 may have no teeth 712.

[0299] The Extended Outer Sleeve 700 is entirely a new invention such ashas never existed in the art or science of surgery, the Extended OuterSleeve 700 offers numerous advantages over all previously describeddrilling sleeves and the Outer Sleeve 140 herein previously described.The Extended Outer Sleeve 700 by dint of its extended portions 720 and722 which are inserted between the adjacent vertebrae does itself act asan intervertebral distractor and is therefore essentially a combinationouter sleeve and distractor. The Extended Outer Sleeve 700 isexceedingly stable as the extended portions 720 and 722 are trappedwithin the disc space and further held there by the considerablecompressive loads within the spine.

[0300] Referring to FIG. 28, because of the stability thus provided, afurther derivative advantage is that the teeth 772 on the distal end 710of the Extended Outer Sleeve 700′ may either be eliminated as shown inFIG. 28, or in the preferred embodiment be made of a lesser size.Further, it should be noted that teeth 712 when present would beconfined to the area directly in line with the vertebrae V and theextended portions 720 and 722 would ensure the proper rotatoryalignment.

[0301] A further advantage, to be discussed in more detail subsequently,is that the extended portions 720 and 722 confine the surgery to thearea within and between the extended portions 720 and 722 and protectall other tissues external to the extended portions 720 and 722.

[0302] Having now described the novel concept of the Extended OuterSleeve 700, attention may now be directed to further variations of theExtended Outer Sleeve 700 capable of not only restoring and maintainingthe appropriate intervertebral disc space height, but additionally beingable to restore and maintain anatomic lordosis or kyphosis, as desired,throughout the surgical procedure.

[0303] Referring to FIG. 29, a Posterior Lordotic Extended Outer Sleeve800 for use from the posterior approach of the spine is shown. ThePosterior Lordotic Extended Outer Sleeve 800 comprises a hollow tubularmember 802 having a distal end 810 which has been extended such that apair of extended portions 820 and 822, which are essentially acontinuation of the tubular member 802, are opposed 180 degrees fromeach other. The extended portions 820 and 822 differ from the extendedportions 720 and 722 in that the extended portions 820 and 822 areconfigured to restore and maintain lordosis of the spine similar to thedisc penetrating portion 420 of the Posterior Long Lordotic Distractor400, the features of which are herein incorporated by reference.

[0304] The extended portions 820 and 822 each have a height that islesser at a point proximate the distal end 810 of the tubular member 802that increases in the direction away from the tubular member 802. Theextended portions 820 and 822 are tapered at their leading edges 824 and826, respectively to facilitate insertion into the disc space.

[0305] Between the extended portions 820 and 822, may be a plurality ofteeth 812 for engaging the bone of the vertebrae V when the ExtendedOuter Sleeve 800 is inserted within the disc space between the adjacentvertebrae V.

[0306] Referring to FIG. 30, a Posterior Lordotic Extended Outer Sleeve800′ in place within the intervertebral disc space is shown.

[0307] Referring to FIG. 31, an Anterior Extended Outer Sleeve 900 foruse from the anterior approach of the spine is shown. The AnteriorLordotic Extended Outer Sleeve 900 comprises a hollow tubular member 902having a distal end 910 which has been extended such that a pair ofextended portions 920 and 922 which are essentially a continuation ofthe tubular member 902 and are opposed 180 degrees from each other. Theextended portions 920 and 922 differ from the extended portions 820 and822 in that the extended portions 920 and 922 are configured to restoreand maintain lordosis of the spine from the anterior approach similar tothe disc penetrating portion 620 of the Anterior Long LordoticDistractor 600, the features of which are herein incorporated byreference.

[0308] The extended portions 920 and 922 each have a height that isgreater at-a point proximate to the distal end 910 of the tubular member902 that decreases in the direction away from the tubular member 902.The extended portions 920 and 922 are tapered at their leading edges 924and 926, respectively to facilitate insertion into the disc space.

[0309] While the Lordotic Extended Outer Sleeve for use anteriorly isshown in the singular form and in use in the lumbar spine, it isunderstood that it may take a double barrelled form and in either form,be used throughout the spine.

[0310] Referring to FIGS. 33 and 34, a Lumbar Dual Extended Outer Sleeveis shown and generally referred to by the numeral 1100. The DualExtended Cuter Sleeve 1100 comprises two hollow tubular members 1101 and1102. The two hollow tubular members 1101 and 1102 have a distal end1104 which has been extended to form an extended portion 1121 which isessentially a continuation of the hollow tubular members 1101 and 1102joined together. The extended portion 1121 is similar in shape andfunction to the extended portions 920 and 922 described above inreference to FIG. 31. The extended portion 1121 has a height that isgreater at a point proximate the distal end 1104 and decreases in thedirection away from the hollow tubular members 1101 and 1102, in orderto maintain the normal curvature of the spine by correcting the angularrelationships of the vertebrae V. The extended portion 1121, is taperedat its leading edge 1124 to facilitate insertion of the extended portion1121 into the disc space between two adjacent vertebrae V. Located atthe distal end of the tubular members 1101 and 1102 are sharpened teeth1130 for engaging the vertebrae V.

[0311] Each of the hollow tubular members 1101 and 1102 are displacedfrom each other ideally the sum of the difference between the minor andmajor diameters of two threaded spinal implants I combined, but not lessthan that difference for one implant I, as it is possible to have thethreads of one implant I nest interposed to the threads of the otherimplant I such that they both occupy a common area between them.Typically, the walls of each hollow tubular members 1101 and 1102 have acombined thickness at the point which the walls of the hollow tubularmembers 1101 and 1102 are in contact with each other which isapproximately 2.0 mm. This is achieved by machining away part of eachhollow tubular member 1101 and 1102 to reduce the wall thickness of eachhollow tubular member 1101 and 1102 prior to joining them together. Inthis manner, the two hollow tubular members 1101 and 1102 may be placedcloser together so that two spinal implants I may be placed closertogether when inserted within the disc space between adjacent vertebraeW. The hollow tubular member 1101 and 1102 can be overlapped ordisplaced from each other so as to control the distance between implantswhen the Dual Extended Outer Sleeve is utilized and two implantsimplanted

[0312] The hollow tubular members 1101 and 1102 may be bridged in partor wholly throughout their length, but are typically fixed by a footplate 1110, similar in function, but not in configuration, to Foot Plate344 described above in reference to FIGS. 7C and 7D.

[0313] Referring specifically to FIG. 34, the foot plate 1110 has anoval configuration that contours and hugs the vertebrae and has aplurality of prongs 1112-1115 extending from the bottom of the footplate 1110 is shown. The prongs 1112-1115 are sufficiently long toengage the bone of adjacent vertebrae V, but limited in length so as notto over penetrate beyond the vertebrae once inserted.

[0314] Referring to FIG. 35, a second Dual Extended Outer Sleeve 1200,is shown. The Dual Extended Outer Sleeve 1200 is similar to the DualExtended Outer Sleeve 1100, except that it has additional extendedportions 1220 and 1222 which have a height that is greater near thedistal end 1204 of the hollow tubular members 1201 and 1202 anddecreases in the direction away from the hollow tubular members 1201 and1202. The extended portions 1220-1222 are similar in shape and functionto the extended portions 920 and 922 described above in reference toFIG. 31. Moreover, as the foot plate 1210 is rectangular and larger thanfoot plate 1110, additional prong 1216 and 1217 may be added.

[0315] Further, it should be appreciated that the Lordotic distractorfor use posteriorly when referring to their use in the lumbar spine,would be used anteriorly if applied to the thoracic spine, either in thesingle or double-barrel form. This is because the thoracic spine isnormally curved into kyphosis which is the reverse of lordosis. That is,in approaching the thoracic spine anteriorly, it would be desirable todistract the back of the disc space more than the front, and that wouldrequire an Extended Outer Sleeve which would resemble that seen in FIG.30; though when used in this new context, it would more correctly bereferred to as an Anterior Thoracic Kyphotic Extended Outer Sleeve. Aswith the Posterior Lordotic Outer Sleeve, the Posterior and AnteriorLong Lordotic Posterior Short Lordotic Distractor and Anterior ShortLordotic Distractors, though referred to previously as Lordotic whenplaced into the lumbar spine from the posterior approach, would now morecorrectly, when placed in the thoracic spine from the anterior approachbe called Kyphotic Thoracic Distractors.

[0316] It can readily be appreciated that the described Extended OuterSleeves may be used with the Short and Long Distractors having a discpenetrating portion of uniform diameter or in combination with thelordotic and kyphotic distractors of complimentary configuration.

[0317] Referring to FIGS. 36-41, shown is the apparatus 1350 for use ininstalling an improved interbody spinal fusion implant 1300 having oneor more flat sides as disclosed in co-pending application filed on Feb.17, 1995, entitled IMPROVED INTERBODY SPINAL FUSION IMPLANTS which isincorporated herein by reference. The apparatus 1350 comprises a DualOuter Sleeve 1310 having a pair of overlapping, hollow cylindrical tubes1352 and 1354 identical in size and each having an internal diameterslightly larger than the outer diameter of the spinal fusion implant1300. The cylindrical tubes 1352, 1354 are in communication with eachother along their length and are displaced from each other ideally adistance that is slightly greater than the sum of the diameters of twospinal fusion implants 1300 placed side-by-side with the flat sides 1302of each spinal fusion implant 1300 touching. The cylindrical tubes 1352and 1354 are joined longitudinally such that they are partiallyoverlapping. The hollow cylindrical tubes 1352 and 1354 are mounted on afoot plate 1362 similar to the foot plate described in FIG. 35. Thereare a series of prongs 1364 a-1364 f projecting from the bottom 1366 ofthe foot plate 1360 which are used to engage the Dual Outer Sleeve 1310to the base of the adjacent vertebrae V.

[0318] Referring specifically to FIG. 36, the apparatus 1350 isintroduced over two Long Distractors 1320 and 1322 placed side-by-sideand protruding anteriorly from the vertebrae V. The Long Distractors1320 and 1322 are similar to the Long Distractor 100 described aboveexcept that they have a flat side 1324 and 1326, respectively.

[0319] Referring to FIGS. 37 and 38, in one embodiment, the foot plate1360 is essentially rectangular, but without sharp corners. It isappreciated by those skilled in the art, that other shapes can beutilized.

[0320] As shown in FIGS. 36 and 39, the foot plate 1360 is contoured soas to approximate the external curvature of the vertebrae V anteriorly.Extending forward from foot plate 1360 are the multiple sharp prongs1364 a-1364 f which are sufficiently long to permit fixation of the footplate 1360 to the vertebrae V. The prongs 1364 a-1364 f are limited inlength so as to not penetrate the vertebrae V too far posteriorly andnumber from 2 to 10, but preferably 6.

[0321] Referring to FIG. 39, as the Dual Outer Sleeve 1350 is drivenforward, the prongs 1364 a-1364 f extending from foot plate 1360 areembedded into the opposed vertebrae V until their forward motion isinhibited by the foot plate 1360 becoming congruent to and being stoppedby, the anterior aspect of the vertebrae V.

[0322] As shown in FIG. 36, once the apparatus 1350 has been fullyseated, the vertebrae V adjacent the interspace D to be fused arerigidly held via foot plate 1360 and the prongs 1364 a-1364 f. Thus, itis possible to remove either one, or if desired, both of the longdistractors 1320 and 1322. The dual outer sleeve has been describedabove for inserting two implants each having at least one flat side, mayhave extended portions for intradiscal insertion which are capable ofproducing distraction as well as kyphosis or lordosis as previouslydescribed with such extensions extending in line with the lateral wallsof the cylindrical tubes.

[0323] Referring to FIG. 40, once the Dual Outer Sleeve 1350 has beenfully seated, one of the Long Distractors 1320 and 1322 is removed andthe surgeon may drill the interspace D utilizing drill 250 using each ofthe hollow cylinders 1352, 1354 to guide the drill 250 in order tocreate overlapping holes in which the spinal fusion implants 1300 a and1300 b may be inserted. It is also appreciated by those skilled in theart, that a hollow inner sleeve (not shown) may be inserted into thehollow cylinders 1352, 1354 through which the drilling is performed orthe Long Distractors may be left in place and a hollow trephine thatfits over each of the Long Distractors 1320 and 1322 may be used todrill the interspace D. It is readily appreciated that the tubularmembers can be of a variety of shapes and sizes. Further, the removal ofdisc and bone may be accomplished by the use of a burr, or a chisel ofappropriate shape for that purpose and with or without the use of adrill. The implants would then have shapes appropriate for use in thespaces so formed.

[0324] Referring to FIG. 41, once the interspace D has been drilled, animplant Driver 350 described above is used to insert the spinal fusionimplants 1300 a and 1300 b preferably by linear advancement. The implantdriver instrument 350 may be used to either insert or to remove thespinal fusion implants 1300 a and 1300 b.

[0325] Once affixed to the implant Driver 350, the spinal fusion implant1300 a is then introduced through one of the hollow cylindrical tubes1352,1354 and driven into the interspace D by the application of animpaction force transmitted through the implant driver instrument 350.Once the spinal fusion implant 1300 a is inserted into-the interspace D,the surface roughenings of the outer surface of the spinal fusionimplant 1300 a engage the bone of the vertebrae V and the implant Driver350 is detached from the spinal fusion implant 1300 a. The implantdriver instrument 350 is then withdrawn from the Dual Outer Sleeve 1350and the spinal fusion implant 1300 a is fully installed and inset in theinterspace D as shown in FIG. 41.

[0326] Once a first spinal fusion implant 1300 a is inserted into theinterspace D, a second spinal fusion implant 1300 b is driven into theinterspace D so that the flat side 1302 a or 1302 b of each spinalfusion implant 1300 a and 1300 b are adjacent to each other and aretouching. In this manner, two spinal fusion implants 1300 a and 1300 bare implanted within the interspace D and engage the bone of theadjacent vertebrae V without exceeding the width of the spinal column.It is appreciated that there are other ways that two spinal implants canhave complimentary shapes and that they can be inserted by linearadvancement through a single (both at once) or dual outer sleeve havingintradiscal extended members for stabilization, distraction, and/or toeffect lordosis or kyphosis.

[0327] While the present invention has been described in associationwith the implant of a threaded spinal implant, it is recognized thatother forms of implants may be used with the present method. Forexample, dowels, made from bone or artificial materials, knurled orirregularly shaped cylinders or partial cylinders, or any other shapedimplants that can be introduced through the outer sleeve may be used.Being able to perform the procedure through the outer sleeve permits theprocedure to be performed safely and quickly, and more accurately.

What is claimed is:
 1. Apparatus for use in spinal fusion surgerycomprising a hollow tubular member having at least a first extendedportion for insertion in the disc space between two adjacent vertebrae,said first extended portion providing distraction and alignment of saidtwo adjacent vertebrae.
 2. The apparatus of claim 1 in which said firstextended portion is substantially in line with one of the side surfacesof said hollow tubular member.
 3. The apparatus of claim 1 in which saidhollow tubular member comprises a second extended portion.
 4. Theapparatus of claim 3 in which said first and second extended portionsare diametrically opposed to each other.
 5. The apparatus of claim 1 inwhich said first extended portion has a height that is substantiallyequal to the normal height of the disc space between two adjacentvertebrae.
 6. The apparatus of claim 1 in which said first extendedportion has a height that increases in the direction away from saidhollow tubular member.
 7. The apparatus of claim 6 in which said firstextended portion comprises a tapered leading edge.
 8. The apparatus ofclaim 1 in which said extended portion has a height that decreases inthe direction away from the hollow tubular member.
 9. The apparatus ofclaim 1 in which said hollow tubular member comprises a distal end thatis contoured to the curvature of said two adjacent vertebrae to permitan intimate fit between said hollow tubular member and said two adjacentvertebrae.
 10. The apparatus of claim 1 further including bone engagingmeans for engaging the bone of said two adjacent vertebrae.
 11. Theapparatus of claim 10 in which said bone engaging means comprises aplurality of teeth for insertion into said adjacent vertebrae.
 12. Theapparatus of claim 10 in which said bone engaging means comprises atleast one prong for insertion into said adjacent vertebrae.
 13. Theapparatus of claim 1 further including penetration preventing means forpreventing over penetration of said pair of extended portions.
 14. Theapparatus of claim 1 including a removable hollow inner tubular sleeve.15. The apparatus of claim 14 in which said inner sleeve has a collar atone end larger than the inside diameter of said hollow tubular member.16. The apparatus of claim 1 in which said hollow tubular member has anincreased outer diameter portion at its upper end.
 17. The apparatus ofclaim 16 including a cap, said cap having an opening in one end havingan inside diameter larger than the outside diameter of said increaseddiameter portion of said member.
 18. A spinal distractor, comprising adisc penetrating portion for insertion in the disc space betweenadjacent vertebrae, said disc penetrating portion having an unevendiameter.
 19. The spinal distractor of claim 18 including a barrelmember extending from said disc penetrating portion.
 20. The spinaldistractor of claim 19 including a shoulder at the juncture of said discpenetrating portion and said barrel member for preventing said barrelmember from entering the disc space.
 21. The spinal distractor of claim18 in which said disc penetrating portion includes a bullet-shaped frontend to facilitate insertion in the disc space.
 22. The spinal distractorof claim 18 in which said uneven diameter of said disc penetratingportion is lesser at its proximal end and greater in a direction towardits distal insertion end.
 23. The spinal distractor of claim 22 in whichsaid disc penetrating portion includes a bullet-shaped front end at saiddistal insertion end to facilitate insertion into the disc space. 24.The spinal distractor of claim 18 in which said uneven diameter of saiddisc penetrating portion is greater at its proximal end and lesser inthe direction towards its distal insertion end.
 25. The spinaldistractor of claim 24 in which said disc penetrating portion includes abullet-shaped front end at said distal insertion end to facilitateinsertion in the disc space.
 26. The spinal distractor of claim 19 inwhich said barrel member is removably attached to said disc penetratingportion.
 27. The spinal distractor of claim 26 in which said discpenetrating portion includes a head portion for engaging said adjacentvertebrae and limiting the depth of insertion of said disc penetratingportion.
 28. Apparatus for use in performing surgery for fusingvertebrae comprising a pair of hollow tubular extended outer sleeves andhaving at least one extended portion for insertion in the disc spacebetween two adjacent vertebrae.
 29. The apparatus of claim 28 in whichsaid hollow tubular member includes at least a second extended portion.30. The apparatus of claim 28 in which said hollow tubular extendedouter sleeves are couple to a depth limiting foot plate.
 31. Theapparatus of claim 28 including engagement means at one end for engagingadjacent vertebrae.
 32. The apparatus of claim 28 in which saidengagement means comprises prongs.
 33. The apparatus of claim 31 inwhich said engagement means are located on a foot plate attached to saidhollow tubular extended outer sleeves.
 34. Apparatus for use inperforming surgery for fusing vertebrae comprising a pair of hollowtubular members joined together partially overlapping along theirlongitudinal axis.
 35. The apparatus of claim 34 in which said pair ofhollow tubular members have at least one extended portion for insertionin the disc space between two adjacent vertebrae.
 36. The apparatus ofclaim 34 in which said hollow tubular members include a second extendedportion.
 37. The apparatus of claim 34 in which said hollow tubularmembers are rigidly fixed by a foot plate.
 38. The apparatus of claim 34including engagement means at one end for engaging adjacent vertebrae.39. The apparatus of claim 38 in which said engagement means comprisesprongs.
 40. The apparatus of claim 38 in which said engagement means arelocated on a foot plate attached to said hollow tubular members.
 41. Amethod for inserting a spinal implant between two adjacent vertebraecomprising inserting a hollow tubular extended outer sleeve having meansfor engaging the spine; removing at least a portion of a spinal disclocated between two adjacent vertebrae; inserting an implant in thevertebrae through said tubular extended outer sleeve; and then removingsaid tubular extended outer sleeve.
 42. The method of claims 42 in whichsaid means for engaging the spine includes at least one extended portionfor insertion in the disc space between two adjacent vertebrae.
 43. Themethod of claim 42 including the steps of passing a boring means throughsaid hollow tubular extended outer sleeve to bore a hole across the discspace and into a portion of the two adjacent vertebrae; removing theboring means.
 44. The method of claim 43 in which said boring means is adrill.
 45. The method of claims 43 in which said boring means istrephine.
 46. The method of claim 41 in which said step for inserting animplant comprises inserting one or more at least partially cylindricalimplants.
 47. The method of claim 43 further including the step ofinserting a removable hollow inner sleeve into said hollow tubularextended outer sleeve prior to passing said drill through said hollowtubular extended outer sleeve.
 48. The method of claim 47 in which theinside diameter of the hollow inner sleeve is equal to the root diameterof a threaded implant.
 49. The method of claim 47 in which the insidediameter of the hollow inner sleeve is slightly greater than the rootdiameter of a threaded implant.
 50. The method claim 41 in which anendoscope is used during at least a portion of said method.
 51. Themethod claim 41 in which a radiographic imaging device is used during atleast a portion of said method.
 52. A method for inserting a spinalimplant between two adjacent vertebrae, comprising the steps of:inserting a spinal distractor in the disc space between two vertebrae toprovide for proper spacing of the disc space between the vertebrae, saidspinal distractor comprising a barrel member terminating in a discpenetrating portion having an uneven diameter; inserting over the spinaldistractor a hollow tubular member having at least a first extendedportion for maintaining distraction of the adjacent vertebrae, saidextended portion having an uneven height; removing the spinal distractorfrom the hollow tubular member; passing a boring means through thehollow tubular member to bore a hole in the disc and a portion of thetwo adjacent vertebrae; removing the boring means; inserting an implantin the vertebrae through the hollow tubular member; and removing saidhollow tubular member.
 53. The method of claims 52 in which said boringmeans is a drill.
 54. The method of claim 52 in which said boring meansis a trephine.
 55. The method of claim 52 in which said implant is atleast partially cylindrical.
 56. The method of claim 52 in which saiduneven diameter of said disc penetrating is lesser proximate said barrelmember and greater in the direction away from said barrel member. 57.The method of claim 56 in which said uneven height of said extendedportion increases in a direction away from said hollow tubular member.58. The method of claim 57 in which said disc penetrating portionincludes a bullet-shaped front end to facilitate insertion of said discpenetrating portion in the disc space.
 59. The method of claim 52 inwhich said uneven diameter of said disc penetrating portion of saidspinal distractor is greater proximate said barrel member and lesser inthe direction away from said barrel member.
 60. The method of claim 59in which said uneven height of said extended portions of said hollowtubular member increases in a direction away from said hollow tubularmember.
 61. The method of claim 52 in which said disc penetratingportion includes a bullet-shaped front end to facilitate insertion ofsaid disc penetrating portion in the disc space.
 62. A method forinserting a spinal implant between two adjacent vertebra comprising:inserting a spinal distractor having a disc penetrating portion with anuneven diameter in the disc space between two adjacent vertebrae torestore and maintain the normal angular relationship of the adjacentvertebrae; placing over said spinal distractor and engaging to the spinea hollow tubular member having an engagement means for engaging thespine and for maintaining distraction of the adjacent vertebrae; passinga trephine through the hollow tubular member and over the spinaldistractor to drill a hole across the disc space and into a portion ofthe two adjacent vertebrae; removing the trephine; removing the spinaldistractor; inserting an implant in the vertebrae through the hollowtubular member; and removing said hollow tubular member.
 63. The methodof claim 62 in which said trephine has means associated therewith forlimiting the depth of the drilling.
 64. A method for inserting a spinalimplant between two adjacent vertebrae, comprising the steps of:inserting at least one spinal distractor in the disc space between twovertebrae to provide for proper spacing of the disc space between thevertebrae; inserting over said spinal distractor a pair of hollowtubular extended outer sleeves, said hollow tubular extended outersleeves having at least one extended portion for insertion in the discspace between two adjacent vertebrae for maintaining distraction of theadjacent vertebrae; removing said spinal distractor from said pair ofhollow tubular extended outer sleeves; passing a drill through each ofsaid pair of hollow tubular extended outer sleeves to drill holes acrossthe disc space and into a portion of the two adjacent vertebrae;removing the drill; inserting at least one implant into the vertebraethrough said pair of hollow tubular extended outer sleeves; and removingsaid pair of hollow tubular extended outer sleeves.
 65. The method ofclaim 64 in which said hollow tubular extended outer sleeves comprise asecond extended portion.
 66. The method of claim 65 in which said firstand second extended portions are diametrically opposed to each other.67. The method of claim 64 in which said extended portion has an unevenheight.
 68. The method of claim 64 in which each of said plurality ofimplants is cylindrical.
 69. The method of claim 64 in which said spinaldistractor has a disc penetrating portion with an uneven diameter. 70.The method of claim 69 in which said uneven diameter of said discpenetrating portion is lesser proximate said barrel member and greaterin the direction away from said barrel member.
 71. The method of claim64 in which said disc penetrating portion includes a bullet-shaped frontend to facilitate insertion in the disc space.
 72. The method of claim69 in which said uneven diameter of said disc penetrating portion isgreater proximate said barrel member and lesser in the direction awayfrom said barrel member.
 73. The method of claim 72 in which said discpenetrating portion includes a bullet-shaped front end to facilitateinsertion in the disc space.
 74. The method of claim 67 in which saiduneven height of said extended portion is lesser proximate said barrelmember and greater in the direction away from said barrel member. 75.The method of claim 67 in which said uneven height of said extendedportion is greater proximate said barrel member and lesser in thedirection away from said barrel member.
 76. The method of claim 64 inwhich said pair of hollow tubular extended outer sleeves are coupled toa depth limiting foot plate.
 77. The method of claim 76 in which saidfoot plate includes engagement means at one end for engaging theadjacent vertebrae.
 78. A method for inserting a spinal implant betweentwo adjacent vertebrae comprising inserting a pair of hollow tubularextended outer sleeves, said hollow tubular extended outer sleeveshaving at least one extended portion for insertion in the disc spacebetween two adjacent vertebrae for maintaining distraction of the twoadjacent vertebrae; passing a drill through each of said pair of hollowtubular extended outer sleeves to drill holes across the disc space andinto a portion of the two adjacent vertebrae; removing the drill;inserting a plurality of implants into the vertebrae; and removing saidpair of tubular extended outer sleeves.
 79. The method of claim 78 inwhich said implants are at least in part cylindrical.
 80. The method ofclaim 80 further including the step of insertion a removable hollowinner sleeve into each of said pair of hollow tubular extended outersleeves.
 81. The method of claim 80 in which the inside diameter of thehollow inner sleeve is the same diameter as the root diameter of each ofthe implants.
 82. The method of claim 80 in which the inside diameter ofthe hollow inner sleeve is slightly greater than the root diameter ofeach of the implants.
 83. The method of claim 78 in which said drill hasmeans associated therewith for limiting the depth of the drilling. 84.The method of claim 78 in which said depth limiting means is lockablyadjustable.
 85. The method of claim 78 in which said implant is made ofbone.
 86. The method of claim 78 in which said implant is made of amaterial that promotes bone ingrowth.
 87. The method of claim 78 inwhich said implant comprises a fusion promoting material.
 88. The methodof claim 78 in which said hole drilled across the disc space and into aportion of the adjacent vertebrae is tapped with a thread.
 89. Themethod of claim 88 in which said hole is drilled through a hollow innersleeve and said hollow inner sleeve is removed prior to tapping saidhole.
 90. The method of claim 84 in which the inside diameter of thehollow inner sleeve is the same diameter as the root diameter of theimplant.
 91. The method of claim 84 in which the inside diameter of thehollow inner sleeve is slightly greater than the root diameter of theimplant.
 92. A method for inserting a spinal implant between twoadjacent vertebrae comprising the steps of: (1) inserting a firstdistractor in the disc space between the two adjacent vertebrae andinserting a second distractor beside said first dis-tractor to providefor proper spacing of the disc space between the vertebrae; (2) placingover said first and second distractors a hollow tubular member havingmeans for engaging said two vertebrae; (3) removing said firstdistractor; passing a drill through said hollow tubular member to drilla hole in the disc and a portion of the two adjacent vertebrae; (4)removing the drill; (5) inserting an implant in the vertebrae throughsaid hollow, tubular member; (6) removing said hollow tubular member;(7) removing said second distractor; and repeating steps (3) through(6).
 93. A method for securing a hollow tubular sleeve to two adjacentvertebrae comprising: inserting at least one spinal distractor into thedisc space intermediate two adjacent vertebrae, said distractor having adepth limiting means; placing an outer sleeve having at least onetubular member and having on one end engagement means for engaging twoadjacent vertebrae over said distractor, said distractor serving as acentering post and as an alignment rod for said outer sleeve; drivingsaid outer sleeve towards the spine over said distractor to engage saidengaging means to the spine; and removing said distractor with adistractor pulling means leaving said outer sleeve in place.
 94. Themethod of claim 93 in which said outer sleeve includes penetrationpreventing means for preventing overpenetration of said engaging means.95. The method of claim 94 in which said penetration preventing means islockably adjustable.
 96. A method for inserting a spinal implant betweentwo adjacent vertebrae, comprising the steps of: inserting a spinaldistractor in the disc space between two vertebrae to provide for properspacing of the disc space between the vertebrae, said spinal distractorcomprising a barrel member terminating in a disc penetrating portion;inserting over the spinal distractor a hollow tubular member having atleast a first extended portion for maintaining distraction of theadjacent vertebrae, said extended portion having an uneven height;removing the spinal distractor from the hollow tubular member; passing aboring means through the hollow tubular member to bore a hole in thedisc and a portion of the two adjacent vertebrae; removing the boringmeans; inserting an implant in the vertebrae through the hollow tubularmember; and. removing said hollow tubular member.
 97. The method ofclaims 96 in which said boring means is a drill.
 98. The method of claim96 in which said boring means is a trephine.
 99. The method of claim 96in which said implant is at least partially cylindrical.
 100. The methodof claim 96 in which said uneven height of said extended portionincreases in a direction away from said hollow tubular member.
 101. Themethod of claim 96 in which said disc penetrating portion includes abullet-shaped front end to facilitate insertion of said disc penetratingportion in the disc space.
 102. The method of claim 96 in which saiduneven height of said extended portions of said hollow tubular memberincreases in a direction away from said hollow tubular member.
 103. Amethod for inserting a plurality of partially cylindrical spinal fusionimplants made of a material appropriate for human implantation, each ofsaid plurality of implants comprising a cylinder having a longitudinalcentral axis and at least one flat side parallel to said central axis,said implant having a maximum diameter larger than the disc spacebetween two adjacent vertebrae, comprising the steps of: drilling twopartially overlapping cylindrical holes across the disc space betweenthe two adjacent vertebrae; inserting a first of said partiallycylindrical spinal fusion implants having a first flat side into one ofsaid overlapping cylindrical holes, said first flat side being orientedperpendicular to the plane of said disc space; inserting a second ofsaid partially cylindrical implants having a second flat side into asecond of said overlapping holes, said second flat side being adjacentand facing said first flat side of said first implant.
 104. A method forinserting a plurality of partially cylindrical spinal fusion implantsmade of a material appropriate for human implantation, each of saidplurality of implants comprising a cylinder having a longitudinalcentral axis and at least one flat side parallel to said central axis,said implant having a diameter larger than the disc space between twoadjacent vertebrae, said disc space being in a plane perpendicular tothe longitudinal vertical axis of the spinal column, comprising thesteps of: drilling two partially overlapping cylindrical holes acrossthe disc space between the two adjacent vertebrae; inserting a first ofsaid partially cylindrical spinal fusion implants having a first flatside into one of said overlapping cylindrical holes, said first flatside being oriented perpendicular to the plane of said disc space;inserting a second of said partially cylindrical implants having asecond flat side into a second of said overlapping holes, said secondflat side being adjacent and facing said first flat side of the firstimplant.